Co-reporter:Meirong Zhang;Zhitong Jin;Chuanqi Feng;Min Wang
Journal of Materials Chemistry A 2017 vol. 5(Issue 32) pp:16976-16983
Publication Date(Web):2017/08/15
DOI:10.1039/C7TA04717G
To enhance the ionic conductivity of imidazolium iodide based ionic conductors, the π conjugation of the imidazolium cation is expanded via N-substitution with aromatic groups of phenyl and thienyl. Three ionic conductors (ICs) of MPhII, MT2II and MT3II are designed and synthesized by linking benzene, 2-thiophene, and 3-thiophene to the imidazolium ring, respectively, and their single crystal structures are revealed. Quasi-solid-state electrolytes are prepared by solidifying the IC-containing solutions with SiO2 nanoparticles for quasi-solid-state dye-sensitized solar cells (QSS-DSSCs). The ionic conductivity of these quasi-solid-state electrolytes depends on the substituent and the substitution position as well, which correlates well with the distance between adjacent iodides, as revealed by the crystal packing structures. Owing to the highest conductivity among the three electrolytes, the QSS-DSSC with the MPhII based quasi-solid-state electrolyte achieves the highest power conversion efficiency of 8.36% under AM 1.5G sunlight (100 mW cm−2), which also exhibits good long-term stability under one sun soaking for more than 2000 h.
Co-reporter:Shanshan Chen, Songwang Yang, Hong Sun, Lu Zhang, Jiajun Peng, Ziqi Liang, Zhong-Sheng Wang
Journal of Power Sources 2017 Volume 353(Volume 353) pp:
Publication Date(Web):15 June 2017
DOI:10.1016/j.jpowsour.2017.03.144
•Doping of CoSe into PCBM can enhance the conductivity.•Doping of CoSe can improve interfacial electron extraction.•Doping of CoSe can reduce interfacial charge transfer resistance.•Doping of CoSe can enhance short-circuit photocurrent and fill factor remarkably.•Doping of CoSe can increase power conversion efficiency by 30%.To improve the electron transfer at the interface between the perovskite film and the electron-transporting-material (ETM) layer, CoSe doped [6,6]-phenyl C61-butyric acid methyl ester (PCBM) is employed as the ETM layer for the inverted planar perovskite solar cell with NiO as the hole-transporting-material layer. Introduction of CoSe (5.8 wt%) into the PCBM layer improves the conductivity of the ETM layer and decreases the photoluminescence intensity, thus enhancing the interfacial electron extraction and reducing the electron transfer resistance at the perovskite/ETM interface. As a consequence, the power conversion efficiency is enhanced from 11.43% to 14.91% by 30% due to the noted increases in short-circuit current density from 17.95 mA cm−2 to 19.85 mA cm−2 and fill factor from 0.60 to 0.70. This work provides a new strategy to improve the performance of inverted perovskite solar cells.Download high-res image (183KB)Download full-size image
Co-reporter:Hong Sun;Gang Wang
Chinese Journal of Chemistry 2017 Volume 35(Issue 5) pp:645-650
Publication Date(Web):2017/05/01
DOI:10.1002/cjoc.201600411
AbstractCo9Se8 nanosheets are synthesized via a solvothermal reaction. Thin films of Co9Se8 nanosheets are respectively fabricated through drop-cast and in situ growth for use as the electrocatalyst in dye-sensitized solar cells (DSSCs). Comparative studies reveal that the in situ growth Co9Se8 nanosheets film exhibits higher electrocatalytic activity for the electrocatalytic reduction of triiodide to iodide and better electrochemical stability than the drop-casted film. When applied as the counter electrode in DSSCs, the in situ growth film yields higher power conversion efficiency (8.65%) than the drop-casted film (5.87%) and even outperforms the reference Pt electrode (8.16%) under comparable conditions.
Co-reporter:Mingyang Cha; Peimei Da; Jun Wang; Weiyi Wang; Zhanghai Chen; Faxian Xiu; Gengfeng Zheng
Journal of the American Chemical Society 2016 Volume 138(Issue 27) pp:8581-8587
Publication Date(Web):June 26, 2016
DOI:10.1021/jacs.6b04519
To improve the interfacial charge transfer that is crucial to the performance of perovskite solar cells, the interface engineering in a device should be rationally designed. Here we have developed an interface engineering method to tune the photovoltaic performance of planar-heterojunction perovskite solar cells by incorporating MAPbBr3–xIx (MA = CH3NH3) quantum dots (QDs) between the MAPbI3 perovskite film and the hole-transporting material (HTM) layer. By adjustment of the Br:I ratio, the as-synthesized MAPbBr3–xIx QDs show tunable fluorescence and band edge positions. When the valence band (VB) edge of MAPbBr3–xIx QDs is located below that of the MAPbI3 perovskite, the hole transfer from the MAPbI3 perovskite film to the HTM layer is hindered, and hence, the power conversion efficiency decreases. In contrast, when the VB edge of MAPbBr3–xIx QDs is located between the VB edge of the MAPbI3 perovskite film and the highest occupied molecular orbital of the HTM layer, the hole transfer from the MAPbI3 perovskite film to the HTM layer is well-facilitated, resulting in significant improvements in the fill factor, short-circuit photocurrent, and power conversion efficiency.
Co-reporter:Lu Zhang and Zhong-Sheng Wang
Journal of Materials Chemistry A 2016 vol. 4(Issue 16) pp:3614-3620
Publication Date(Web):22 Mar 2016
DOI:10.1039/C6TC00592F
Gold nanoparticles of various sizes have been prepared and deposited on top of the TiO2 film in dye-sensitized solar cells (DSSCs) in order to enhance the light harvesting efficiency. The light scattering effect gradually strengthens as the size of Au nanoparticles increases from 48 to 203 nm. It is impressive that 1 μg cm−2 deposition of 203 nm gold nanoparticles on top of the TiO2 film enhances the light scattering efficiency remarkably, increasing the short-circuit photocurrent from 14.37 mA cm−2 to 17.81 mA cm−2 by 24% and the power conversion efficiency from 7.44% to 10.03% by 35%.
Co-reporter:Kai Lv, Wei Zhang, Lu Zhang, and Zhong-Sheng Wang
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 8) pp:5343
Publication Date(Web):February 10, 2016
DOI:10.1021/acsami.5b12353
To expand the application of solid-state dye-sensitized solar cells (ssDSSCs) to low temperatures, it is necessary to develop new solid electrolytes with low glass transition temperature (Tg). The Tg is regulated by varying the length of alkyl chain that is connected with the nitrogen atom in the imidazolium ring linked to the polyhedral oligomeric silsesquioxane (POSS). The Tg as low as −8.8 °C is achieved with the POSS grafted with methyl-substituted imidazolium. The effect of alkyl group on the conductivity, Tg, and photovoltaic performance has also been investigated. The conductivity and power conversion efficiency increase with the alkyl length, while the Tg first increases and then decreases with the alkyl length. Among the synthesized POSS-based ionic conductors, the POSS grafted with the methyl-substituted imidazolium yields the highest power conversion efficiency of 6.98% at RT due to its highest conductivity, and the efficiency (6.52%) is still good at −4 °C, as its Tg (−8.8 °C) is lower than the working temperature (−4 °C). This finding suggests that the POSS-based solid electrolyte is promising for subzero-temperature applications of ssDSSCs.Keywords: alkyl length effect; dye-sensitized solar cells; low temperature operation; POSS; solid-state electrolyte
Co-reporter:Suhua Fan, Xuefeng Lu, Hong Sun, Gang Zhou, Yuan Jay Chang and Zhong-Sheng Wang
Physical Chemistry Chemical Physics 2016 vol. 18(Issue 2) pp:932-938
Publication Date(Web):27 Nov 2015
DOI:10.1039/C5CP05986K
To obtain a broad spectral response in the visible region, TiO2 film is co-sensitized with a porphyrin dye (FNE57 or FNE59) and an organic dye (FNE46). It is found that the stepwise co-sensitization in one single dye solution followed by in another single dye solution is better than the co-sensitization in a cocktail solution in terms of photovoltaic performance. The stepwise co-sensitization first with a porphyrin dye and then with an organic dye outperforms that in a reverse order. DSSC devices based on co-sensitizers FNE57 + FNE46 and FNE59 + FNE46 with a quasi-solid-state gel electrolyte generate power conversion efficiencies of 7.88% and 8.14%, respectively, which exhibits remarkable efficiency improvements of 61% and 35%, as compared with devices sensitized with the porphyrin dyes FNE57 and FNE59, respectively. Co-sensitization brings about a much improved short-circuit photocurrent due to the complementary absorption of the two sensitizers. The observed enhancement of incident monochromatic photon-to-electron conversion efficiency from individual dye sensitization to co-sensitization is attributed to the improved charge collection efficiency rather than to the light harvesting efficiency. Interestingly, the open-circuit photovoltage for the co-sensitization system comes between the higher voltage for the porphyrin dye (FNE57 or FNE59) and the lower voltage for the organic dye (FNE46), which is well correlated with their electron lifetimes. This finding indicates that not only the spectral complementation but also the electron lifetime should be considered to select dyes for co-sensitization.
Co-reporter:Peimei Da, Mingyang Cha, Lu Sun, Yizheng Wu, Zhong-Sheng Wang, and Gengfeng Zheng
Nano Letters 2015 Volume 15(Issue 5) pp:3452-3457
Publication Date(Web):April 27, 2015
DOI:10.1021/acs.nanolett.5b00788
Lead halide perovskites have achieved phenomenal successes in photovoltaics due to their suitable bandgaps, long diffusion lengths, and balanced charge transport. However, the extreme susceptibility of perovskites to water or air has imposed a seemingly insurmountable barrier for leveraging these unique materials into solar-to-fuel applications such as photoelectrochemical conversion. Here we developed a CH3NH3PbI3-based photoanode with an ultrathin Ni surface layer, which functions as both a physical passivation barrier and a hole-transferring catalyst. Remarkably, a much enhanced photocurrent density, an unassisted photoelectrochemical conversion capability, and a substantially better stability against water have been achieved, which are exceeding most of the previously reported photoanodes as well as a similar CH3NH3PbI3-based device structure but without the Ni surface layer. Our study suggests many exciting opportunities of developing perovskite-based solar-to-fuel conversion.
Co-reporter:Yan Cui, Lu Zhang, Kai Lv, Gang Zhou and Zhong-Sheng Wang
Journal of Materials Chemistry A 2015 vol. 3(Issue 8) pp:4477-4483
Publication Date(Web):15 Jan 2015
DOI:10.1039/C4TA06679K
Nanoparticle chains of anatase TiO2 composed of ∼5 nm nanoparticles with a high surface area (309 m2 g−1) are prepared by slow hydrolysis of titanium tetraisopropoxide modified with glacial acetic acid at a temperature of 50 °C. These nanoparticle chains without hydrothermal treatment can be used directly to fabricate photoanodes for highly efficient dye-sensitized solar cells (DSSCs), which achieve a power conversion efficiency of 9.80% at simulated AM1.5 G illumination (100 mW cm−2). The approach presented in this study demonstrates a facile synthesis of anatase TiO2 chains for use in DSSCs, which avoid hazards arising from a hydrothermal process that is typically adopted to prepare crystalline TiO2 nanoparticles for use as the photoanode in DSSCs.
Co-reporter:Lu Zhang, Hong Sun, Zhaosheng Xue, Bin Liu and Zhong-Sheng Wang
Journal of Materials Chemistry A 2015 vol. 3(Issue 33) pp:17042-17049
Publication Date(Web):15 Jul 2015
DOI:10.1039/C5TA04877J
To retard charge recombination efficiently in dye-sensitized solar cells (DSSCs), an ultrathin film of single-crystal titania nanosheets is pre-coated on a conductive substrate as a blocking layer through electrostatic layer-by-layer self-assembly. The marked effect of the self-assembled titania nanosheet film is the remarkable enhancements of short-circuit photocurrent by 45%, from 12.57 to 18.24 mA cm−2, and open-circuit photovoltage by 16%, from 690 to 798 mV. As a consequence, the power conversion efficiency is improved notably by 61% from 6.50% to 10.48% when a 50 nm thick titania nanosheet film is pre-coated as a blocking layer, which is also superior to that obtained by using a pyrolyzed blocking layer (7.79%) and the well-known TiCl4 treatment (efficiency of 7.98%). Controlled intensity modulated photovoltage/photocurrent spectra reveal that the self-assembled blocking layer of titania nanosheets not only retards charge recombination but also increases the charge collection efficiency, accounting for the remarkable increase in open-circuit photovoltage and short-circuit photocurrent, respectively. This finding implies that pre-deposition of an ultrathin TiO2 nanosheet layer on the conductive substrate would be an ideal strategy to remarkably increase short-circuit photocurrent and open-circuit photovoltage simultaneously and thus to enhance the power conversion efficiency of DSSCs remarkably.
Co-reporter:Shanshan Chen, Lei Lei, Songwang Yang, Yan Liu, and Zhong-Sheng Wang
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 46) pp:25770
Publication Date(Web):November 2, 2015
DOI:10.1021/acsami.5b07511
The properties of perovskite films are sensitive to the fabrication method, which plays a crucial role in the performance of perovskite solar cell. In this work, we fabricate organo-lead iodide perovskite on mesoporous TiO2 films through two different two-step deposition methods, respectively, for the purpose of studying the crystal growth of perovskite film and its effect on light harvesting efficiency, defect density, charge extraction rate, and energy levels. The crystal growth exerts a significant influence on the morphology and hence the film properties, which are found to correlate with the performance of solar cells. It is found that vapor deposition of methylammonium iodide in the PbI2 lattice gives a more complete coverage on mesoporous TiO2 with a flatter surface and Fermi level closer to the middle of the band-gap, resulting in higher light absorption in the visible spectral region, lower defect density, and faster charge extraction, as compared to the sequential solution deposition. For this reason, the vapor-processed perovskite film achieves higher short-circuit photocurrent and power conversion efficiency than the solution-processed film.Keywords: crystal growth engineering; energy level; light harvesting; perovskite solar cell; time-resolved photoluminescence decay
Co-reporter:Gang Wang, Hong Sun, Lu Ding, Gang Zhou and Zhong-Sheng Wang
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 37) pp:24361-24369
Publication Date(Web):24 Aug 2015
DOI:10.1039/C5CP03748D
A simple and versatile hydrothermal method is developed to synthesize Cu–Cu2O, in which Cu particles grow on the surface of a Cu2O truncated octahedron. Through the reduction of Cu2+ by glucose in an alkaline solution, the Cu2O truncated octahedron is quickly formed via a kinetic control process, and then Cu particles selectively nucleate on the high-energy (110) facets of Cu2O, generating a heterostructure. The amount of Cu in the sample is successfully tuned by varying the reaction temperature. Compared to Cu2O, the hybrid Cu–Cu2O architecture shows superior electrocatalytic performance for glucose oxidation due to the synergistic effect between more electrocatalytic active but less conductive Cu2O and more conductive but less electrocatalytic active Cu. By tuning the content of Cu in the heterostructure, the highest electrocatalytic activity is achieved at the Cu/Cu2O molar ratio of 0.83.
Co-reporter:Juan Li and Zhong-Sheng Wang
RSC Advances 2015 vol. 5(Issue 70) pp:56967-56973
Publication Date(Web):24 Jun 2015
DOI:10.1039/C5RA09688J
A new solid-state ionic conductor is synthesized by linking an ether group to the nitrogen-atom of 1,2-dimethylimidazole with an iodide counter anion, and the single crystal structure is determined using X-ray crystallographic analysis. Replacement of the butyl group in 1-butyl-2,3-dimethylimidazolium iodide with an ether group induces a significant improvement in conductivity. When the solid ionic conductor is mixed with LiI alone, conductivity enhancement is more remarkable for the ether-containing ionic conductor due to the lithium coordination to the ether oxygen, which is able to avoid the aggregation of lithium cations with iodides and hence improves the transport properties of Li+. Owing to the π-stacking of imidazolium rings for the ether-containing ionic conductor, the increment of ionic conductivity is also more significant upon further doping with I2. The ether-containing ionic conductor mixed with LiI alone as the solid electrolyte can even make the solid-state dye-sensitized solar cells work. Further doping with iodine achieves power conversion efficiency of 7.1%, which is much higher than that (5.3%) for the alkyl analogue due to the positive shift of the conduction band edge of titanium dioxide and suppression of charge recombination caused by the ether group.
Co-reporter:Shenghui Jiang, Suhua Fan, Xuefeng Lu, Gang Zhou and Zhong-Sheng Wang
Journal of Materials Chemistry A 2014 vol. 2(Issue 40) pp:17153-17164
Publication Date(Web):18 Aug 2014
DOI:10.1039/C4TA03451A
Three double D–π–A branched organic dye isomers (D1, D2, and D3) with octyloxy bridge linked at different positions of the π-bridge in the D–π–A branch have been designed and synthesized for dye-sensitized solar cells (DSSCs). Their photophysical, electrochemical, and photovoltaic properties were further investigated. Compared with the reference dye isomers containing single D–π–A branches, the double D–π–A branched dye isomers consisting of two separated light-harvesting moieties in one molecule are beneficial to photocurrent generation. Moreover, the cross structure of the double D–π–A branched organic dye isomers is superior to the rod structure of the dye isomers with single D–π–A branches in the suppression of intermolecular interactions, which results in reduced charge recombination rates in the DSSCs based on double branched organic dye isomers. Therefore, in comparison to the DSSCs based on isomeric dyes with single D–π–A branches, the DSSCs based on double branched organic dye isomers display both improved short-circuit current and open-circuit voltage. Furthermore, similar to the single D–π–A branched organic dye isomers, those isomeric dyes with double D–π–A branches exhibit slightly different photophysical properties, which result in the varied photovoltaic performance. The highest power conversion efficiency of 8.1% and 6.9%, respectively, is achieved for isomer D1 based DSSC with liquid and quasi-solid-state electrolyte under simulated AM1.5G solar irradiation (100 mW cm−2).
Co-reporter:Hong Sun, Lu Zhang and Zhong-Sheng Wang
Journal of Materials Chemistry A 2014 vol. 2(Issue 38) pp:16023-16029
Publication Date(Web):30 Jul 2014
DOI:10.1039/C4TA02238F
Single-crystal CoSe2 nanorods have been prepared by a facile one-step hydrothermal method. The thin CoSe2 films fabricated by drop-casting the CoSe2 nanorod suspension onto conductive substrates followed by simple drying without sintering can be used as a highly efficient electrocatalyst for the reduction of I3−. Dye-sensitized solar cells (DSSCs) with the standard N719 dye and the single-crystal CoSe2 nanorod cathode achieve a power conversion efficiency of 10.20% under AM1.5G one-sun illumination versus 8.17% for the Pt cathode. This finding implies that single-crystal CoSe2 nanorods are promising low-cost and high-performance cathode materials for high-performance DSSCs.
Co-reporter:Wei Zhang, Juan Li, Shenghui Jiang and Zhong-Sheng Wang
Chemical Communications 2014 vol. 50(Issue 14) pp:1685-1687
Publication Date(Web):16 Dec 2013
DOI:10.1039/C3CC48615J
Polyhedral oligomeric silsesquioxane functionalized with eight imidazolium iodide arms has been designed and synthesized for use as solid-state electrolytes in solid-state dye-sensitized solar cells, which exhibits a power conversion efficiency of 7.11% under one sun illumination and good long-term stability under one sun soaking.
Co-reporter:Juan Li, Wei Zhang, Lu Zhang and Zhong-Sheng Wang
Physical Chemistry Chemical Physics 2014 vol. 16(Issue 16) pp:7334-7338
Publication Date(Web):04 Mar 2014
DOI:10.1039/C4CP00628C
To minimize the charge recombination between electrons and the electron acceptor in solid-state dye-sensitized solar cells, we propose a separated electron donor and acceptor of a redox couple in the photoanode and in the cathode, respectively. Owing to the absence of the acceptor in the photoanode initially, the charge recombination rate is retarded remarkably, resulting in an increase of the short-circuit photocurrent by >2-fold, open-circuit photovoltage by 71 mV and power conversion efficiency by >2.5-fold.
Co-reporter:Yan Li, Hong Wang, Quanyou Feng, Gang Zhou and Zhong-Sheng Wang
Energy & Environmental Science 2013 vol. 6(Issue 7) pp:2156-2165
Publication Date(Web):26 Apr 2013
DOI:10.1039/C3EE23971C
By designing a fine-controlled nanocomposite with Au nanoparticles (∼2 nm in size) directly inlaid in TiO2 as working electrode, efficiency (η) of 10.1% for a dye-sensitized solar cell with an open-circuit photovoltage of 863 mV and a short-circuit photocurrent of 15.71 mA cm−2 have been achieved, giving an enhancement of 97 mV in photovoltage, 63% in photocurrent and 84% in efficiency compared to the cell with pure TiO2 photoanode (η = 5.5%). As compared to pure TiO2, besides the local-field optical enhancement near the TiO2 surface caused by plasma resonance of Au nanoparticles which increases the dye absorption and hence the amount of photogenerated charge contributing to the photocurrent, it is evidenced that not only the quasi-Fermi level of Au–TiO2 photoanode can be modulated to more negative potentials by controlling the mass ratio of Au–TiO2, but their mosaic nanostructure reduces the charge recombination rate effectively, both leading to a marked enhancement of photovoltage. Our results prove that the unique nanostructural, physical and chemical properties of the direct mosaic nanoarchitecture of ∼2 nm Au and TiO2 make them valuable materials as working electrodes for DSSCs to achieve high photovoltage and hence further improve the performance.
Co-reporter:Hong Wang ; Juan Li ; Feng Gong ; Gang Zhou
Journal of the American Chemical Society 2013 Volume 135(Issue 34) pp:12627-12633
Publication Date(Web):August 2, 2013
DOI:10.1021/ja401827w
Imidazolium iodide is an often used component in iodine-based dye-sensitized solar cells (DSSCs), but it cannot operate an efficient DSSC in the absence of iodine due to its low conductivity. For this study, lamellar solid iodide salts of imidazolium or piperidinium with an N-substituted propargyl group have been prepared and applied in solid-state DSSCs. Owing to the high conductivity arising from the lamellar structure, these solid-state ionic conductors can be used as single-component solid electrolytes to operate solid-state DSSCs efficiently without any additives in the electrolyte and post-treatments on the dye-loaded TiO2 films. With a propargyl group attached to the imidazolium ring, the conductivity is enhanced by about 4 × 104-fold as compared to the alkyl-substituted imidazolium iodide. Solid-state DSSC with the 1-propargyl-3-methylimidazolium iodide as the single-component solid-state electrolyte has achieved a light-to-electricity power conversion efficiency of 6.3% under illumination of simulated AM1.5G solar light (100 mW cm–2), which also exhibits good long-term stability under continuous 1 sun soaking for 1500 h. This finding paves the way for development of high-conductivity single-component solid electrolytes for use in efficient solid-state DSSCs.
Co-reporter:Yan Li, Quanyou Feng, Hong Wang, Gang Zhou and Zhong-Sheng Wang
Journal of Materials Chemistry A 2013 vol. 1(Issue 21) pp:6342-6349
Publication Date(Web):21 Mar 2013
DOI:10.1039/C3TA10520B
Polypyridine complexes of Co(II)/Co(III) coupled with donor–π bridge–acceptor structured organic dyes are by far the most promising route to boost the efficiency of dye-sensitized solar cells (DSSCs). We report herein the first investigation of Ta3N5 nanorods incorporated on reduced graphene oxide (RGO) sheets as a counter electrode for application in Co(bpy)33+/2+ (bpy = 2,2′-bipyridine) mediated DSSCs. RGO–Ta3N5 composite was fabricated by mixing graphene oxide (GO) with pre-synthesized Ta3N5 nanorods (aspect ratio of ∼3) followed by facile hydrazine hydrate reduction. The composite film on conductive glass was prepared by a drop-casting process at room temperature without heat treatment. Compared with a Pt cathode with a power conversion efficiency of 7.59%, RGO–Ta3N5 exhibited comparable electrocatalytic performance for the reduction of Co(bpy)33+ species and better electrocatalytic stability in Co(bpy)33+/2+ acetonitrile solution, which was attributed to the synergetic catalytic effect of RGO and Ta3N5 nanorods and the high electrical conductivity derived from the RGO network, resulting in a power conversion efficiency of 7.85%. The present result is expected to lead to a family of composites for highly efficient cathode materials.
Co-reporter:Hong Wang, Quanyou Feng, Feng Gong, Yan Li, Gang Zhou and Zhong-Sheng Wang
Journal of Materials Chemistry A 2013 vol. 1(Issue 1) pp:97-104
Publication Date(Web):05 Nov 2012
DOI:10.1039/C2TA00705C
To improve the electrocatalytic performance of polyaniline thin films, an oriented polyaniline nanowires array has been successfully grown in situ on conductive glass substrates without templates and applied as the cathode of dye-sensitized solar cells (DSSCs) mediated with a Co(bpy)33+/2+ (bpy = 2,2′-bipyridine) redox couple. Compared to the polyaniline film with a random network, the oriented polyaniline nanowires array exhibits much better electrocatalytic performance, and even outperforms the typical Pt electrode in both electrocatalytic performance and electrochemical stability when exposed to the acetonitrile solution of the Co(bpy)33+/2+ redox couple. Owing to the higher electrocatalytic performance, the DSSC with the oriented nanowires array produces a higher short-circuit photocurrent and fill factor than the DSSCs with the random polyaniline network or Pt cathodes. Consequently, the power conversion efficiency of DSSCs based on a typical D–π–A organic dye sensitizer increases from 5.97% for the polyaniline random network cathode to 8.24% for the oriented polyaniline nanowires array cathode, which is also higher than the efficiency (6.78%) of the DSSC with the Pt cathode.
Co-reporter:Quanyou Feng, Xiaowei Jia, Gang Zhou and Zhong-Sheng Wang
Chemical Communications 2013 vol. 49(Issue 67) pp:7445-7447
Publication Date(Web):26 Jun 2013
DOI:10.1039/C3CC44258F
An electron donor and acceptor, respectively, is embedded into naphtho[2,1-b:3,4-b′]dithiophene based organic sensitizers to tune their optoelectronic properties. The DSSC based on FNE52 containing an auxiliary electron acceptor displays a maximum power conversion efficiency of 8.2% and good long-term stability.
Co-reporter:Quanyou Feng, Qian Zhang, Xuefeng Lu, Hong Wang, Gang Zhou, and Zhong-Sheng Wang
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 18) pp:8982
Publication Date(Web):August 27, 2013
DOI:10.1021/am402036j
Two sets of isomeric organic dyes with n-hexyl (DH and AH) or 2-ethylhexyl (DEH and AEH) groups substituted at the spacer part have been designed and straightforwardly synthesized via a facile and selective synthetic route. The structure difference between the isomers stands at the position of the incorporated alkyl chains which are introduced into the terthiophene spacer close to the donor (D) or anchor (A) side. The relationship between the isomeric structures and the optoelectronic properties are systematically investigated. It is found that, in the D series dyes, the alkyl group is much closer to the aromatic donor moiety, which brings about strong steric hindrance and therefore causes a remarkable twist in the molecular skeleton. In contrast, a more planar chemical structure and more effective π-conjugation are realized in the A series dye isomers. Consequently, the A series isomeric dyes demonstrate bathochromically shifted absorption bands, resulting in the improved light-harvesting capability and enhanced photo-generated current. However, the D series isomeric dyes with more twisted molecular skeleton have suppressed the intermolecular interactions and retarded the charge recombination more efficiently, which induces higher open-circuit photovoltage. Combining the two effects on the performance of the fabricated dye-sensitized solar cells (DSSC), the influence from the short-circuit photocurrent plays a more significant role on the power conversion efficiency (η). As a result, isomer AEH-based DSSC with quasi-solid-state electrolyte displays the highest η of 7.10% which remained at 98% of the initial value after continuous light soaking for 1000 h. Promisingly, a η of 8.66% has been achieved for AEH-based DSSC with liquid electrolyte containing Co(II)/(III) redox couple. This work presents the crucial issue of molecular engineering and paves a way to design organic sensitizers for highly efficient and stable DSSCs.Keywords: charge recombination; dye-sensitized solar cells; isomers; oligothiophene; quasi-solid state; sensitizers;
Co-reporter:Feng Gong, Xin Xu, Zhuoqun Li, Gang Zhou and Zhong-Sheng Wang
Chemical Communications 2013 vol. 49(Issue 14) pp:1437-1439
Publication Date(Web):21 Dec 2012
DOI:10.1039/C2CC38621F
Nickel diselenide (NiSe2) has been synthesized and applied as a counter electrode (CE) of dye-sensitized solar cells (DSSCs) for the first time, which displays remarkable catalytic activity in the reduction of I3−. The DSSC with a NiSe2 CE produces a higher power conversion efficiency (8.69%) than that (8.04%) of the cell with a Pt CE under the same conditions. A new method for comparing the catalytic activity has also been proposed.
Co-reporter:Shenghui Jiang, Xuefeng Lu, Gang Zhou and Zhong-Sheng Wang
Chemical Communications 2013 vol. 49(Issue 37) pp:3899-3901
Publication Date(Web):22 Mar 2013
DOI:10.1039/C3CC00159H
Two novel cross-conjugated isomers based on 4,8-dithienylbenzo[1,2-b:4,5-b′]dithiophene have been designed and successfully synthesized. It was found that the charge transfer interaction was much stronger in the benzodithiophene direction as compared with the other perpendicular direction.
Co-reporter:Juan Li, Hong Wang, Gang Zhou and Zhong-Sheng Wang
Chemical Communications 2013 vol. 49(Issue 82) pp:9446-9448
Publication Date(Web):16 Aug 2013
DOI:10.1039/C3CC44940H
Hydroxyethyl and ester co-functionalized imidazolium iodide has been designed and synthesized as an efficient solid state electrolyte for dye-sensitized solar cells. Single crystal X-ray analyses confirm the presence of ordered three dimensional ionic channels for iodide, which exhibits high conductivity when mixed with iodine and LiI and achieves a power conversion efficiency of 7.45%.
Co-reporter:Yan Li, Hong Wang, Quanyou Feng, Gang Zhou, and Zhong-Sheng Wang
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 16) pp:8217
Publication Date(Web):July 15, 2013
DOI:10.1021/am402353m
We report herein the investigation of TaON nanoparticles incorporating a reduced graphene oxide (RGO) nanocomposite as a counter electrode for application in Co(bpy)33+/2+ (bpy = 2,2′-bipyridine)-mediated dye-sensitized solar cells (DSSCs). The RGO–TaON nanocomposite has been prepared by mixing graphene oxide (GO) and presynthesized TaON nanoparticles in ethanol/water followed by the facile hydrazine hydrate reduction of GO to RGO. Compared with RGO or TaON alone, the RGO–TaON nanocomposite shows a much higher electrocatalytic activity for the reduction of Co(bpy)33+ species owing to synergistic effects, resulting in significantly improved solar-cell performance when it is applied as the counter electrode in DSSCs. An efficiency of 7.65% for the DSSC with the RGO–TaON counter electrode is obtained, competing with the efficiency produced by the Pt counter electrode; additionally, the former exhibits a much better electrochemical stability than the latter in a Co(bpy)33+/2+ acetonitrile solution.Keywords: Co(bpy)33+/2+ redox couple; counter electrode; dye-sensitized solar cell; reduced graphene oxide−TaON nanocomposite;
Co-reporter:Xin Xu, Hong Wang, Feng Gong, Gang Zhou, and Zhong-Sheng Wang
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 8) pp:3219
Publication Date(Web):March 19, 2013
DOI:10.1021/am4002293
Linking an ester group to the imidazolium ring has been demonstrated to improve solar cell performance in terms of short-circuit photocurrent (Jsc), open-circuit photovoltage (Voc), and fill factor (FF) in particular, when the imidazolium iodide mixed with iodine and LiI is used as a solid state electrolyte of dye-sensitized solar cells. Herein, the effect of ester group on solar cell performance has been investigated by means of intensity modulated photocurrent/photovoltage and electrochemical impedance spectroscopy. From the alkyl- to ester-functionalized imidazolium iodide, the increase in Jsc is attributed to the increased charge collection efficiency due to the enhanced conductivity, the increase in Voc is caused by the upward shift of conduction band edge of TiO2, which compensates for the voltage loss arising from the higher charge recombination rate, and the remarkable increase in FF is attributed to the decreased series resistance along with the increased Voc and decreased diode quality factor.Keywords: charge collection efficiency; dye-sensitized solar cell; electrochemical impedance; ester group; imidazolium iodide;
Co-reporter:Quanyou Feng, Gang Zhou, Zhong-Sheng Wang
Journal of Power Sources 2013 Volume 239() pp:16-23
Publication Date(Web):1 October 2013
DOI:10.1016/j.jpowsour.2013.03.091
•Branched alkyl chains are superior in suppression of charge recombination in DSSC.•Linear alkyl chains are better than branched alkyl chains in photocurrent generation.•A power conversion efficiency of 8.12% was achieved for the DSSC based on FNE29.Suppression of dye aggregation and interfacial charge recombination by appropriate structural modification of the sensitizers is crucial to improve the performance of dye-sensitized solar cells (DSSCs). In this article, linear alkyl chains, i.e., hexyl groups, and branched alkyl chains, i.e., 2-ethylhexyl groups, are introduced into a sensitizer with a terthiophene unit as conjugated bridge. The effects of the linear and branched alkyl chains on the photophysical, electrochemical properties and photovoltaic properties are investigated. By comparison, branched alkyl chains are superior to linear alkyl chains in suppression of intermolecular interactions and the electron recombination between the injected electrons and the electron acceptors in the electrolyte. Consequently, a more significant improvement of the open-circuit photovoltage can be achieved by the introduction of branched alkyl chains to the π-conjugated bridge of the organic dye in comparison to the incorporation of linear alkyl chains. Conversely, linear alkyl chains are better than branched alkyl chains in broadening photoresponse and hence photocurrent generation. As a result, a power conversion efficiency of 8.12% was achieved for the DSSC based on FNE29 with linear alkyl chains.
Co-reporter:Feng Gong, Xin Xu, Gang Zhou and Zhong-Sheng Wang
Physical Chemistry Chemical Physics 2013 vol. 15(Issue 2) pp:546-552
Publication Date(Web):12 Nov 2012
DOI:10.1039/C2CP42790G
In this work, reduced graphene oxide (RGO) sheets are successfully introduced into the conductive polypyrrole (PPy) matrix as conductive channels and co-catalyst, through simple incorporation of graphene oxide (GO) into PPy and subsequent in situ reduction from GO/PPy to RGO/PPy composite film. The RGO/PPy film is fabricated as a counter electrode for dye-sensitized solar cells, and it exhibits excellent catalytic performance for reduction of triiodide. For this reason, the incorporated RGO sheets significantly improve short-circuit photocurrent density from 14.27 to 15.81 mA cm−2 and power conversion efficiency from 7.11% to 8.14%, which is comparable with that for the cell based on a Pt cathode.
Co-reporter:Zhuoqun Li, Feng Gong, Gang Zhou, and Zhong-Sheng Wang
The Journal of Physical Chemistry C 2013 Volume 117(Issue 13) pp:6561-6566
Publication Date(Web):March 9, 2013
DOI:10.1021/jp401032c
NiS2 nanoparticles and nanocomposites of NiS2 with reduced graphene oxide (NiS2@RGO) have been successfully prepared via a facile hydrothermal reaction of nickel ions and sulfur source in the absence or presence of graphene oxide. NiS2@RGO nanocomposites exhibit excellent electrocatalytic performance for reduction of triiodide, owing to the improved conductivity and positive synergetic effect between NiS2 and RGO. As a consequence, the dye-sensitized solar cell with the NiS2@RGO counter electrode (CE) produces a power conversion efficiency of 8.55%, which is higher than that (7.02%) for the DSSC with the NiS2 CE, higher than that (3.14%) for the DSSC with the RGO CE, and also higher than that (8.15%) for the DSSC with the reference Pt CE under the same conditions.
Co-reporter:Hong Wang;Xi Zhang;Feng Gong;Gang Zhou
Advanced Materials 2012 Volume 24( Issue 1) pp:121-124
Publication Date(Web):
DOI:10.1002/adma.201103785
Co-reporter:Yongzhen Wu;Xi Zhang;Wenqin Li;He Tian;Weihong Zhu
Advanced Energy Materials 2012 Volume 2( Issue 1) pp:149-156
Publication Date(Web):
DOI:10.1002/aenm.201100341
Abstract
For a sensitizer with a strong π-conjugation system, a coadsorbent is needed to hinder dye aggregation. However, coadsorption always brings a decrease in dye coverage on the TiO2 surface. Organic ‘‘D–A–π–A’’ dyes, WS-6 and WS-11, are designed and synthesized based on the known WS-2 material for coadsorbent-free, dye-sensitized solar cells (DSSCs). Compared with the traditional D–π–A structure, these D–A–π–A indoline dyes, with the additional incorporated acceptor unit of benzothiadiazole in the π-conjugation, exhibit a broad photoresponse, high redox stability, and convenient energy-level tuning. The attached n-hexyl chains in both dyes are effective to suppress charge recombination, resulting in a decreased dark current and enhanced open-circuit voltage. Electrochemical impedance spectroscopy studies indicate that both the resistance for charge recombination and the electron lifetime are increased after the introduction of alkyl chains to the dye molecules. Without deoxycholic acid coadsorption, the power-conversion efficiency of WS-6 (7.76%) on a 16 μm-thick TiO2 film device is 45% higher than that of WS-2 (5.31%) under the same conditions. The additional n-hexylthiophene in WS-11 extends the photoresponse to a panchromatic spectrum but causes a low incident photon-to-current conversion efficiency.
Co-reporter:Tao Chen, Longbin Qiu, Zhenbo Cai, Feng Gong, Zhibin Yang, Zhongsheng Wang, and Huisheng Peng
Nano Letters 2012 Volume 12(Issue 5) pp:2568-2572
Publication Date(Web):April 13, 2012
DOI:10.1021/nl300799d
Metal wires suffer from corrosion in fiber-shaped dye-sensitized solar cells (DSSCs). We report herein that stable, ultrastrong, and highly flexible aligned carbon nanotube fibers can be used not only as catalytic counter electrodes but also as conductive materials to support dye-loaded TiO2 nanoparticles in DSSCs. The power conversion efficiency of this fiber solar cell can achieve 2.94%. These solar power fibers, exhibiting power conversion efficiency independent of incident light angle and cell length, can be woven into textiles via a convenient weaving technology.
Co-reporter:Feng Gong ; Hong Wang ; Xin Xu ; Gang Zhou
Journal of the American Chemical Society 2012 Volume 134(Issue 26) pp:10953-10958
Publication Date(Web):June 1, 2012
DOI:10.1021/ja303034w
We present herein a facile one-step low-temperature hydrothermal approach for in situ growth of metal selenides (Co0.85Se and Ni0.85Se) on conductive glass substrates. The as-prepared metal selenides on conductive substrates can be used directly as transparent counter electrodes for dye-sensitized solar cells (DSSCs) without any post-treatments. It is found that graphene-like Co0.85Se exhibits higher electrocatalytic activity than Pt for the reduction of triiodide. As a consequence, the DSSC with Co0.85Se generates higher short-circuit photocurrent and power conversion efficiency (9.40%) than that with Pt.
Co-reporter:Xiaoming Ren, Shenghui Jiang, Mingyang Cha, Gang Zhou, and Zhong-Sheng Wang
Chemistry of Materials 2012 Volume 24(Issue 17) pp:3493
Publication Date(Web):August 7, 2012
DOI:10.1021/cm302250y
An organic dye containing two D-π-A branches linked with a thiophene unit has been designed and synthesized for efficient dye-sensitized solar cells (DSSCs). As compared to the rod-shape of the single D-π-A analogue dye, the cross shape of the double D-π-A branched dye is favorable for reducing intermolecular interaction and retarding charge recombination. Controlled intensity modulated photovoltage spectroscopy reveals that electron lifetime for the double D-π-A dye-based DSSC is 14-fold longer than that for the corresponding single D-π-A dye-based DSSC. Linking two D-π-A branches with a thiophene unit increases open-circuit photovoltage by 100 mV and short-circuit photocurrent by 4.10 mA cm–2. As a consequence, power conversion efficiency is enhanced by about 2-fold. This work presents a new route to designing sensitizers with high suppression ability of charge recombination toward high-performance DSSCs.Keywords: charge recombination; double D-π-A organic dye; dye-sensitized solar cells;
Co-reporter:Xuefeng Lu, Quanyou Feng, Tian Lan, Gang Zhou, and Zhong-Sheng Wang
Chemistry of Materials 2012 Volume 24(Issue 16) pp:3179
Publication Date(Web):August 6, 2012
DOI:10.1021/cm301520z
A series of quinoxaline based metal-free organic sensitizers has been designed and synthesized for dye-sensitized solar cells (DSSCs). The absorption, electrochemical, and photovoltaic properties for all sensitizers have been systematically investigated. It is found that the incorporation of quinoxaline unit instead of thienopyrazine unit results in a negative shift of the lowest unoccupied molecular orbital levels for FNE44, FNE45, FNE46, and FNE47, in comparison to FNE32, which induces a remarkable enhancement of the electron injection driving force from the excited organic sensitizers to the TiO2 semiconductor. Moreover, when the alkyl substituents are removed from the spacer part in FNE44 to the donor part in FNE45 and FNE46, a more conjugated system and a bathochromically shifted maximum absorption band can be realized, which consequently results in an increased light harvesting efficiency and photogenerated current. In addition, the length of the alkyl substituents on the donor part has a certain influence on the DSSC performance. Combining the three contributions, FNE46-based DSSC with liquid electrolyte displays the highest power conversion efficiency (η) of 8.27%. Most importantly, a η of 7.14% has been achieved for FNE46 based quasi-solid-state DSSC and remained at 100% of the initial value after continuous light soaking for 1000 h, which indicates that FNE46 is appropriate for promising commercial application. Our findings will facilitate the understanding of the crucial importance of molecular engineering and pave a new path to design novel metal-free organic dyes for highly efficient and stable DSSCs.Keywords: charge recombination; dye-sensitized solar cells; organic dye; quasi-solid-state; quinoxaline;
Co-reporter:Feng Gong, Zhuoqun Li, Hong Wang and Zhong-Sheng Wang
Journal of Materials Chemistry A 2012 vol. 22(Issue 33) pp:17321-17327
Publication Date(Web):04 Jul 2012
DOI:10.1039/C2JM33483F
Close-packed graphene suffers from a low surface area, which limits its electrocatalytic activity as the counter electrode in dye-sensitized solar cells (DSSCs). We report herein the synthesis of a porous graphene/SiO2 nanocomposite converted from graphene oxide mixed with SiO2 nanoparticles (∼12 nm) through facile hydrazine hydrate reduction. Graphene and graphene/SiO2 films prepared by drop-casting the suspensions without organic binder or surfactant onto the conductive glass substrates at room temperature without heat treatment have been applied directly as counter electrodes in DSSCs. As compared to the nonporous graphene film, the porous graphene/SiO2 composite film demonstrates much better electrocatalytic performance for the reduction of triiodide in DSSCs due to the remarkably enhanced surface area. As a consequence, the incorporation of SiO2 nanoparticles in the graphene film improves the fill factor and power conversion efficiency by 65% and 69%, respectively. With a 2.5 μm-thick graphene/SiO2 composite film as the counter electrode, the power conversion efficiency of the DSSC achieves 6.82%, which is comparable to that for the DSSC with a Pt counter electrode.
Co-reporter:Quanyou Feng, Xuefeng Lu, Gang Zhou and Zhong-Sheng Wang
Physical Chemistry Chemical Physics 2012 vol. 14(Issue 22) pp:7993-7999
Publication Date(Web):13 Apr 2012
DOI:10.1039/C2CP40872D
Novel organic sensitizers containing a thieno[3,4-c]pyrrole-4,6-dione (TPD) moiety with triphenylamine or julolidine as the electron donor have been designed and synthesized for quasi-solid-state dye-sensitized solar cells (DSSCs). For comparison, two organic dyes based on a terthiophene spacer have also been synthesized. The absorption, electrochemical and photovoltaic properties of all sensitizers have been systematically investigated. We found that the incorporation of TPD is highly beneficial to broaden the absorption spectra of the organic sensitizers and prevent the intermolecular interaction. Therefore, the charge recombination possibility is reduced, which is revealed by the controlled intensity modulated photovoltage spectroscopy. A quasi-solid-state DSSC based on sensitizer FNE38 with TPD and triphenylamine moieties demonstrates a solar energy conversion efficiency of 4.71% under standard AM 1.5G sunlight without the use of coadsorbant agents.
Co-reporter:Shutao Wang, Xi Zhang, Gang Zhou and Zhong-Sheng Wang
Physical Chemistry Chemical Physics 2012 vol. 14(Issue 2) pp:816-822
Publication Date(Web):23 Nov 2011
DOI:10.1039/C1CP23041G
Surface modification plays a crucial role in improving the efficiency of dye-sensitized solar cells (DSSCs), but the reported surface treatments are in general superior to the untreated TiO2 but inferior to the typical TiCl4-treated TiO2 in terms of solar cell performance. This work demonstrates a two-step treatment of the nanoporous titania surface with strontium acetate [Sr(OAc)2] and TiCl4 in order, each step followed by sintering. An electronically insulating layer of SrCO3 is formed on the TiO2 surface via the Sr(OAc)2 treatment and then a fresh TiO2 layer is deposited on top of the SrCO3 layer via the TiCl4 treatment, corresponding to a double layer of Sr(OAc)2/TiO2 coated on the TiO2 surface. As compared to the typical TiCl4-treated DSSC, the Sr(OAc)2–TiCl4 treated DSSC improves short-circuit photocurrent (Jsc) by 17%, open-circuit photovoltage (Voc) by 2%, and power conversion efficiency by 20%. These results indicate that the Sr(OAc)2–TiCl4 treatment is better than the often used TiCl4 treatment for fabrication of efficient DSSCs. Charge density at open circuit and controlled intensity modulated photocurrent/photovoltage spectroscopy reveal that the two electrodes show almost same conduction band level but different electron diffusion coefficient and charge recombination rate constant. Owing to the blocking effect of the SrCO3 layer on electron recombination with I3− ions, the charge recombination rate constant of the Sr(OAc)2–TiCl4 treated DSSC is half that of the TiCl4-treated DSSC, accounting well for the difference of their Voc. The improved Jsc is also attributed to the middle SrCO3 layer, which increases dye adsorption and may improve charge separation efficiency due to the blocking effect of SrCO3 on charge recombination.
Co-reporter:Qiuliu Huang, Gang Zhou, Liang Fang, Lipeng Hu and Zhong-Sheng Wang
Energy & Environmental Science 2011 vol. 4(Issue 6) pp:2145-2151
Publication Date(Web):20 Apr 2011
DOI:10.1039/C1EE01166A
A series of oriented rutile TiO2 nanorod-array films are in-situ grown on fluorine-doped tin oxide (FTO) coated glass substrates from a mixed acid solution containing titanium tetraisopropoxide (TTIP), hydrochloric acid (HCl), acetic acid (HOAc), and water (H2O) by means of hydrothermal reaction at 150 °C. The effect of HOAc in the titania growth solution on the structure and micro-morphology of TiO2 nanorod array films, as well as the photoelectric conversion properties in dye-sensitized solar cells (DSSCs) has been fully investigated. It is found that HOAc can facilitate the formation of uniform, dense, and vertically oriented TiO2 nanorods and hence improves the dye adsorption, electron diffusion coefficient, and the photovoltaic performance of DSSCs, typically in short-circuit photocurrent and power conversion efficiency. A power conversion efficiency of 4.03% has been achieved on a DSSC based on a 2.3 µm-long nanorod array film obtained from a mixed acid solution with the TTIP:HCl:HOAc:H2O ratio of 0.8:4:8:8 by volume.
Co-reporter:Weihong Zhu;Yongzhen Wu;Shutao Wang;Wenqin Li;Xin Li;Jian Chen;He Tian
Advanced Functional Materials 2011 Volume 21( Issue 4) pp:756-763
Publication Date(Web):
DOI:10.1002/adfm.201001801
Abstract
A novel concept “D-A-π-A” organic sensitizer instead of traditional D-π-A ones is proposed. Remarkably, the incorporated low bandgap, strong electron-withdrawing unit of benzothiadiazole shows several favorable characteristics in the areas of light-harvesting and efficiency: i) optimized energy levels, resulting in a large responsive range of wavelengths into NIR region; ii) a very small blue-shift in the absorption peak on thin TiO2 films with respect to that in solution; iii) an improvement in the electron distribution of the donor unit to distinctly increase the photo-stability of synthetic intermediates and final sensitizers. The stability and spectral response of indoline dye-based DSSCs are improved by the strong electron-withdrawing benzothiadizole unit in the conjugation bridge. The incident-photon-conversion efficiency of WS-2 reaches nearly 850 nm with a power conversion efficiency as high as 8.7% in liquid electrolyte and 6.6% in ionic-liquid electrolyte.
Co-reporter:Yan Cui, Yongzhen Wu, Xuefeng Lu, Xi Zhang, Gang Zhou, Fohn B. Miapeh, Weihong Zhu, and Zhong-Sheng Wang
Chemistry of Materials 2011 Volume 23(Issue 19) pp:4394
Publication Date(Web):September 13, 2011
DOI:10.1021/cm202226j
Two novel benzotriazole-containing organic dyes based on D–A−π–A configuration, WS-5 with octyl group and WS-8 with methyl group, have been designed and synthesized for use in dye-sensitized solar cells (DSSCs). Compared with the traditional D−π–A sensitizers, the benzotriazole unit as an additional acceptor has several merits: (i) essentially facilitating the electron transfer from the donor to the acceptor/anchor; (ii) conveniently tailoring the solar cell performance with a facile structural modification on 2-position in the benzotriazole unit; and (iii) the nitrogen-containing heterocyclic group of benzotriazole being expected to improve the open-circuit photovoltage. The analysis of controlled intensity modulated photovoltage spectroscopy reveals that the replacement of methyl with octyl group enhances electron lifetime by 4-fold and retards charge recombination rate constant by 4-fold. The two dye-loaded TiO2 films possess almost the same conduction band position under the same condition, as revealed by the charge densities at open-circuit against open-circuit photovoltage. Therefore, the significant enhancement of open-circuit photovoltage from methyl to octyl group is attributed to the suppressed charge recombination. Under simulated AM1.5G solar light (100 mW cm–2), the DSSC based on WS-5 produces a short-circuit photocurrent of 13.18 mA cm–2, an open-circuit photovoltage of 0.78 V, a fill factor of 0.78, corresponding to a power conversion efficiency of 8.02%.Keywords: benzotriazole; charge recombination; dye sensitizers; open-circuit photovoltage; solar cells;
Co-reporter:Feng Gong, Hong Wang and Zhong-Sheng Wang
Physical Chemistry Chemical Physics 2011 vol. 13(Issue 39) pp:17676-17682
Publication Date(Web):09 Sep 2011
DOI:10.1039/C1CP22542A
Monolayer of PDDA/graphene/PDDA/H2PtCl6 is fabricated on conductive glass using electrostatic layer-by-layer self-assembly technique, which is then converted to graphene/Pt monolayer for use as counter electrode in dye-sensitized solar cell (DSSC). As compared to the sputtered Pt counter electrode, the self-assembled monolayer reduces the Pt amount by about 1000-fold but exhibits comparable photovoltaic performance. This finding provides a new route to fabrication of cheap and efficient counter electrodes for flow-line production of DSSCs.
Co-reporter:Tao Chen;Shutao Wang;Zhibin Yang;Quanyou Feng;Xuemei Sun;Dr. Li Li; Zhong-Sheng Wang; Huisheng Peng
Angewandte Chemie 2011 Volume 123( Issue 8) pp:1855-1859
Publication Date(Web):
DOI:10.1002/ange.201003870
Co-reporter:Xi Zhang ; Fang Liu ; Qiu-Liu Huang ; Gang Zhou
The Journal of Physical Chemistry C 2011 Volume 115(Issue 25) pp:12665-12671
Publication Date(Web):May 26, 2011
DOI:10.1021/jp201853c
W(VI) is doped into TiO2 via a sol–gel method, and the crystalline anatase structure is well preserved with the W content ranging from 0.1% to 5%. The conduction band (CB) of TiO2 moves downward (i.e., positive shift) gradually with increasing the W content from 0.1% to 2% and then stays almost unchanged with increasing the W content from 2% to 5%. Dye-sensitized solar cells (DSSCs) based on the W-doped anatase TiO2 show an advantage in repressing the charge recombination. The electron lifetime in the DSSC is significantly improved by the W-doping. As a result of the positive shift of the CB and repressed charge recombination, the short-circuit photocurrent (Jsc) of the DSSC is improved remarkably. The collective effect of the positive shift of the CB and the enhanced electron lifetime caused by the W-doping makes the open-circuit photovoltage (Voc) remain almost unchanged below 0.5% W-doping and decrease above 0.5% W-doping. The highest power conversion efficiency (η = 9.1%) is obtained at 0.2% W-doping, which shows increases by 17% in Jsc and by 20% in η, as compared with the undoped DSSC.
Co-reporter:Tao Chen;Shutao Wang;Zhibin Yang;Quanyou Feng;Xuemei Sun;Dr. Li Li; Zhong-Sheng Wang; Huisheng Peng
Angewandte Chemie International Edition 2011 Volume 50( Issue 8) pp:1815-1819
Publication Date(Web):
DOI:10.1002/anie.201003870
Co-reporter:Quanyou Feng;Hong Wang;Gang Zhou
Frontiers of Optoelectronics 2011 Volume 4( Issue 1) pp:80-86
Publication Date(Web):2011 March
DOI:10.1007/s12200-011-0209-y
The effect of coadsorption with deoxycholic acid (DCA) on the performance of dye-sensitized solar cell (DSSC) based on [(C4H9)4N]3[Ru(Htcterpy)(NCS)3] (tcterpy = 4,4′,4″-tricarboxy-2,2′:6′,2″-terpyridine), a socalled black dye, had been investigated. Results showed that the coadsorption of DCA with the black dye results in significant improvement in the photocurrent and mild increase in the photovoltage, which leads to an enhancement of overall power conversion efficiency by 9%. The enhancement of photocurrent was attributed to the increased efficiency of charge collection and/or electron injection. The coadsorption with DCA suppressed charge recombination and thus improved open-circuit photovoltage.
Co-reporter:Zhong-Sheng Wang;Fang Liu
Frontiers of Chemistry in China 2010 Volume 5( Issue 2) pp:150-161
Publication Date(Web):2010 June
DOI:10.1007/s11458-010-0113-9
Organic dyes with a D-π-A structure have drawn increasing attention as sensitizers in dye-sensitized solar cells (DSSCs), due to their rich photophysical properties, easy molecular tailoring, and low-cost production. This review mainly focuses on the relationship between dye structure and photovoltaic properties for organic dyes containing cyanoacrylic acid as both an anchor and an acceptor. This review also introduces different donors and π-conjugation units as building blocks for sensitizer synthesis.
Co-reporter:Xiaoming Ren, Quanyou Feng, Gang Zhou, Chun-Hui Huang and Zhong-Sheng Wang
The Journal of Physical Chemistry C 2010 Volume 114(Issue 15) pp:7190-7195
Publication Date(Web):March 31, 2010
DOI:10.1021/jp911630z
This article quantitatively studied the coadsorption effect of deoxycholic acid (DCA) and sodium deoxycholate (DCNa) on the conduction band (CB) shift and charge recombination in dye-sensitized solar cells (DSSC). We found that the degree of the effect varied as the cation differed from H+ to Na+. DCA shifted the CB positively by 26 mV, but DCNa shifted the CB negatively by 33 mV. As compared with the dye-alone-based DSSC, the coadsorption of dye NKX-2677 (2-cyano-3-[5′-(1,1,6,6-tetramethyl-10-oxo-2,3,5,6-tetrahydro-1H,4H,10H-11-oxa-3a-aza-benzo[de]anthracen-9-yl)-[2,2′]bithiophenyl-5-yl]acrylic acid) with DCA retarded the charge recombination rate by 10-fold, corresponding to a 70 mV enhancement of the open-circuit photovoltage (Voc), and the coadsorption of NKX-2677 with DCNa slowed down the charge recombination rate by 3-fold, corresponding to a 37 mV enhancement of Voc. The suppression of charge recombination in combination with CB movement, arising from coadsorption, resulted in a Voc gain of 44 mV (= 70−26 mV) for the DSSC with NKX-2677/DCA and 70 mV (= 37 + 33 mV) for the DSSC with NKX-2677/DCNa. The experimentally observed Voc enhancements of 41 mV by DCA coadsorption and 65 mV by DCNa coadsorption were in good agreement with the calculated improvements.
Co-reporter:Zhong-Sheng Wang and Gang Zhou
The Journal of Physical Chemistry C 2009 Volume 113(Issue 34) pp:15417-15421
Publication Date(Web):August 5, 2009
DOI:10.1021/jp905366t
This paper quantitatively describes how HCl-treatment of nanocrystalline TiO2 films prior to dye adsorption influences charge recombination and conduction band edge movement of dye sensitized solar cells based on dye N749 (the so-called black dye), [(C4H9)4N]3[Ru(Htcterpy)(NCS)3] (tcterpy = 4,4′,4′′-tricarboxy-2,2′:6′,2′′-terpyridine), using intensity modulated photovoltage spectroscopy (IMVS). The surface protonation of TiO2 films causes a positive shift of the conduction band edge by 28 mV, corresponding to a decrease in open-circuit photovoltage (Voc) by 28 mV, and a slower charge recombination rate constant by a factor of 5, corresponding to an increase in Voc by 50 mV. The experimentally observed Voc enhancement (19 mV) by surface protonation of TiO2 films is in good agreement with the collective effect (50 mV − 28 mV = 22 mV) of both a positive shift of the conduction band edge and a slower charge recombination. These data indicate that surface protonation of TiO2 can simultaneously improve Jsc due to the positive shift of conduction band edge and Voc due to the suppression of charge recombination.
Co-reporter:Wei Zhang
ACS Applied Materials & Interfaces () pp:
Publication Date(Web):
DOI:10.1021/am502556y
Replacing liquid-state electrolytes with solid-state electrolytes has been proven to be an effective way to improve the durability of dye-sensitized solar cells (DSSCs). We report herein the synthesis of amorphous ionic conductors based on polyhedral oligomeric silsesquioxane (POSS) with low glass transition temperatures for solid-state DSSCs. As the ionic conductor is amorphous and in the elastomeric state at the operating temperature of DSSCs, good pore filling in the TiO2 film and good interfacial contact between the solid-state electrolyte and the TiO2 film can be guaranteed. When the POSS-based ionic conductor containing an allyl group is doped with only iodine as the solid-state electrolyte without any other additives, power conversion efficiency of 6.29% has been achieved with good long-term stability under one-sun soaking for 1000 h.
Co-reporter:Wei Zhang, Juan Li, Shenghui Jiang and Zhong-Sheng Wang
Chemical Communications 2014 - vol. 50(Issue 14) pp:NaN1687-1687
Publication Date(Web):2013/12/16
DOI:10.1039/C3CC48615J
Polyhedral oligomeric silsesquioxane functionalized with eight imidazolium iodide arms has been designed and synthesized for use as solid-state electrolytes in solid-state dye-sensitized solar cells, which exhibits a power conversion efficiency of 7.11% under one sun illumination and good long-term stability under one sun soaking.
Co-reporter:Feng Gong, Xin Xu, Zhuoqun Li, Gang Zhou and Zhong-Sheng Wang
Chemical Communications 2013 - vol. 49(Issue 14) pp:NaN1439-1439
Publication Date(Web):2012/12/21
DOI:10.1039/C2CC38621F
Nickel diselenide (NiSe2) has been synthesized and applied as a counter electrode (CE) of dye-sensitized solar cells (DSSCs) for the first time, which displays remarkable catalytic activity in the reduction of I3−. The DSSC with a NiSe2 CE produces a higher power conversion efficiency (8.69%) than that (8.04%) of the cell with a Pt CE under the same conditions. A new method for comparing the catalytic activity has also been proposed.
Co-reporter:Shenghui Jiang, Xuefeng Lu, Gang Zhou and Zhong-Sheng Wang
Chemical Communications 2013 - vol. 49(Issue 37) pp:NaN3901-3901
Publication Date(Web):2013/03/22
DOI:10.1039/C3CC00159H
Two novel cross-conjugated isomers based on 4,8-dithienylbenzo[1,2-b:4,5-b′]dithiophene have been designed and successfully synthesized. It was found that the charge transfer interaction was much stronger in the benzodithiophene direction as compared with the other perpendicular direction.
Co-reporter:Quanyou Feng, Xiaowei Jia, Gang Zhou and Zhong-Sheng Wang
Chemical Communications 2013 - vol. 49(Issue 67) pp:NaN7447-7447
Publication Date(Web):2013/06/26
DOI:10.1039/C3CC44258F
An electron donor and acceptor, respectively, is embedded into naphtho[2,1-b:3,4-b′]dithiophene based organic sensitizers to tune their optoelectronic properties. The DSSC based on FNE52 containing an auxiliary electron acceptor displays a maximum power conversion efficiency of 8.2% and good long-term stability.
Co-reporter:Juan Li, Hong Wang, Gang Zhou and Zhong-Sheng Wang
Chemical Communications 2013 - vol. 49(Issue 82) pp:NaN9448-9448
Publication Date(Web):2013/08/16
DOI:10.1039/C3CC44940H
Hydroxyethyl and ester co-functionalized imidazolium iodide has been designed and synthesized as an efficient solid state electrolyte for dye-sensitized solar cells. Single crystal X-ray analyses confirm the presence of ordered three dimensional ionic channels for iodide, which exhibits high conductivity when mixed with iodine and LiI and achieves a power conversion efficiency of 7.45%.
Co-reporter:Lu Zhang, Hong Sun, Zhaosheng Xue, Bin Liu and Zhong-Sheng Wang
Journal of Materials Chemistry A 2015 - vol. 3(Issue 33) pp:NaN17049-17049
Publication Date(Web):2015/07/15
DOI:10.1039/C5TA04877J
To retard charge recombination efficiently in dye-sensitized solar cells (DSSCs), an ultrathin film of single-crystal titania nanosheets is pre-coated on a conductive substrate as a blocking layer through electrostatic layer-by-layer self-assembly. The marked effect of the self-assembled titania nanosheet film is the remarkable enhancements of short-circuit photocurrent by 45%, from 12.57 to 18.24 mA cm−2, and open-circuit photovoltage by 16%, from 690 to 798 mV. As a consequence, the power conversion efficiency is improved notably by 61% from 6.50% to 10.48% when a 50 nm thick titania nanosheet film is pre-coated as a blocking layer, which is also superior to that obtained by using a pyrolyzed blocking layer (7.79%) and the well-known TiCl4 treatment (efficiency of 7.98%). Controlled intensity modulated photovoltage/photocurrent spectra reveal that the self-assembled blocking layer of titania nanosheets not only retards charge recombination but also increases the charge collection efficiency, accounting for the remarkable increase in open-circuit photovoltage and short-circuit photocurrent, respectively. This finding implies that pre-deposition of an ultrathin TiO2 nanosheet layer on the conductive substrate would be an ideal strategy to remarkably increase short-circuit photocurrent and open-circuit photovoltage simultaneously and thus to enhance the power conversion efficiency of DSSCs remarkably.
Co-reporter:Shenghui Jiang, Suhua Fan, Xuefeng Lu, Gang Zhou and Zhong-Sheng Wang
Journal of Materials Chemistry A 2014 - vol. 2(Issue 40) pp:NaN17164-17164
Publication Date(Web):2014/08/18
DOI:10.1039/C4TA03451A
Three double D–π–A branched organic dye isomers (D1, D2, and D3) with octyloxy bridge linked at different positions of the π-bridge in the D–π–A branch have been designed and synthesized for dye-sensitized solar cells (DSSCs). Their photophysical, electrochemical, and photovoltaic properties were further investigated. Compared with the reference dye isomers containing single D–π–A branches, the double D–π–A branched dye isomers consisting of two separated light-harvesting moieties in one molecule are beneficial to photocurrent generation. Moreover, the cross structure of the double D–π–A branched organic dye isomers is superior to the rod structure of the dye isomers with single D–π–A branches in the suppression of intermolecular interactions, which results in reduced charge recombination rates in the DSSCs based on double branched organic dye isomers. Therefore, in comparison to the DSSCs based on isomeric dyes with single D–π–A branches, the DSSCs based on double branched organic dye isomers display both improved short-circuit current and open-circuit voltage. Furthermore, similar to the single D–π–A branched organic dye isomers, those isomeric dyes with double D–π–A branches exhibit slightly different photophysical properties, which result in the varied photovoltaic performance. The highest power conversion efficiency of 8.1% and 6.9%, respectively, is achieved for isomer D1 based DSSC with liquid and quasi-solid-state electrolyte under simulated AM1.5G solar irradiation (100 mW cm−2).
Co-reporter:Lu Zhang and Zhong-Sheng Wang
Journal of Materials Chemistry A 2016 - vol. 4(Issue 16) pp:NaN3620-3620
Publication Date(Web):2016/03/22
DOI:10.1039/C6TC00592F
Gold nanoparticles of various sizes have been prepared and deposited on top of the TiO2 film in dye-sensitized solar cells (DSSCs) in order to enhance the light harvesting efficiency. The light scattering effect gradually strengthens as the size of Au nanoparticles increases from 48 to 203 nm. It is impressive that 1 μg cm−2 deposition of 203 nm gold nanoparticles on top of the TiO2 film enhances the light scattering efficiency remarkably, increasing the short-circuit photocurrent from 14.37 mA cm−2 to 17.81 mA cm−2 by 24% and the power conversion efficiency from 7.44% to 10.03% by 35%.
Co-reporter:Suhua Fan, Xuefeng Lu, Hong Sun, Gang Zhou, Yuan Jay Chang and Zhong-Sheng Wang
Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 2) pp:NaN938-938
Publication Date(Web):2015/11/27
DOI:10.1039/C5CP05986K
To obtain a broad spectral response in the visible region, TiO2 film is co-sensitized with a porphyrin dye (FNE57 or FNE59) and an organic dye (FNE46). It is found that the stepwise co-sensitization in one single dye solution followed by in another single dye solution is better than the co-sensitization in a cocktail solution in terms of photovoltaic performance. The stepwise co-sensitization first with a porphyrin dye and then with an organic dye outperforms that in a reverse order. DSSC devices based on co-sensitizers FNE57 + FNE46 and FNE59 + FNE46 with a quasi-solid-state gel electrolyte generate power conversion efficiencies of 7.88% and 8.14%, respectively, which exhibits remarkable efficiency improvements of 61% and 35%, as compared with devices sensitized with the porphyrin dyes FNE57 and FNE59, respectively. Co-sensitization brings about a much improved short-circuit photocurrent due to the complementary absorption of the two sensitizers. The observed enhancement of incident monochromatic photon-to-electron conversion efficiency from individual dye sensitization to co-sensitization is attributed to the improved charge collection efficiency rather than to the light harvesting efficiency. Interestingly, the open-circuit photovoltage for the co-sensitization system comes between the higher voltage for the porphyrin dye (FNE57 or FNE59) and the lower voltage for the organic dye (FNE46), which is well correlated with their electron lifetimes. This finding indicates that not only the spectral complementation but also the electron lifetime should be considered to select dyes for co-sensitization.
Co-reporter:Feng Gong, Xin Xu, Gang Zhou and Zhong-Sheng Wang
Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 2) pp:NaN552-552
Publication Date(Web):2012/11/12
DOI:10.1039/C2CP42790G
In this work, reduced graphene oxide (RGO) sheets are successfully introduced into the conductive polypyrrole (PPy) matrix as conductive channels and co-catalyst, through simple incorporation of graphene oxide (GO) into PPy and subsequent in situ reduction from GO/PPy to RGO/PPy composite film. The RGO/PPy film is fabricated as a counter electrode for dye-sensitized solar cells, and it exhibits excellent catalytic performance for reduction of triiodide. For this reason, the incorporated RGO sheets significantly improve short-circuit photocurrent density from 14.27 to 15.81 mA cm−2 and power conversion efficiency from 7.11% to 8.14%, which is comparable with that for the cell based on a Pt cathode.
Co-reporter:Feng Gong, Hong Wang and Zhong-Sheng Wang
Physical Chemistry Chemical Physics 2011 - vol. 13(Issue 39) pp:NaN17682-17682
Publication Date(Web):2011/09/09
DOI:10.1039/C1CP22542A
Monolayer of PDDA/graphene/PDDA/H2PtCl6 is fabricated on conductive glass using electrostatic layer-by-layer self-assembly technique, which is then converted to graphene/Pt monolayer for use as counter electrode in dye-sensitized solar cell (DSSC). As compared to the sputtered Pt counter electrode, the self-assembled monolayer reduces the Pt amount by about 1000-fold but exhibits comparable photovoltaic performance. This finding provides a new route to fabrication of cheap and efficient counter electrodes for flow-line production of DSSCs.
Co-reporter:Shutao Wang, Xi Zhang, Gang Zhou and Zhong-Sheng Wang
Physical Chemistry Chemical Physics 2012 - vol. 14(Issue 2) pp:NaN822-822
Publication Date(Web):2011/11/23
DOI:10.1039/C1CP23041G
Surface modification plays a crucial role in improving the efficiency of dye-sensitized solar cells (DSSCs), but the reported surface treatments are in general superior to the untreated TiO2 but inferior to the typical TiCl4-treated TiO2 in terms of solar cell performance. This work demonstrates a two-step treatment of the nanoporous titania surface with strontium acetate [Sr(OAc)2] and TiCl4 in order, each step followed by sintering. An electronically insulating layer of SrCO3 is formed on the TiO2 surface via the Sr(OAc)2 treatment and then a fresh TiO2 layer is deposited on top of the SrCO3 layer via the TiCl4 treatment, corresponding to a double layer of Sr(OAc)2/TiO2 coated on the TiO2 surface. As compared to the typical TiCl4-treated DSSC, the Sr(OAc)2–TiCl4 treated DSSC improves short-circuit photocurrent (Jsc) by 17%, open-circuit photovoltage (Voc) by 2%, and power conversion efficiency by 20%. These results indicate that the Sr(OAc)2–TiCl4 treatment is better than the often used TiCl4 treatment for fabrication of efficient DSSCs. Charge density at open circuit and controlled intensity modulated photocurrent/photovoltage spectroscopy reveal that the two electrodes show almost same conduction band level but different electron diffusion coefficient and charge recombination rate constant. Owing to the blocking effect of the SrCO3 layer on electron recombination with I3− ions, the charge recombination rate constant of the Sr(OAc)2–TiCl4 treated DSSC is half that of the TiCl4-treated DSSC, accounting well for the difference of their Voc. The improved Jsc is also attributed to the middle SrCO3 layer, which increases dye adsorption and may improve charge separation efficiency due to the blocking effect of SrCO3 on charge recombination.
Co-reporter:Quanyou Feng, Xuefeng Lu, Gang Zhou and Zhong-Sheng Wang
Physical Chemistry Chemical Physics 2012 - vol. 14(Issue 22) pp:NaN7999-7999
Publication Date(Web):2012/04/13
DOI:10.1039/C2CP40872D
Novel organic sensitizers containing a thieno[3,4-c]pyrrole-4,6-dione (TPD) moiety with triphenylamine or julolidine as the electron donor have been designed and synthesized for quasi-solid-state dye-sensitized solar cells (DSSCs). For comparison, two organic dyes based on a terthiophene spacer have also been synthesized. The absorption, electrochemical and photovoltaic properties of all sensitizers have been systematically investigated. We found that the incorporation of TPD is highly beneficial to broaden the absorption spectra of the organic sensitizers and prevent the intermolecular interaction. Therefore, the charge recombination possibility is reduced, which is revealed by the controlled intensity modulated photovoltage spectroscopy. A quasi-solid-state DSSC based on sensitizer FNE38 with TPD and triphenylamine moieties demonstrates a solar energy conversion efficiency of 4.71% under standard AM 1.5G sunlight without the use of coadsorbant agents.
Co-reporter:Juan Li, Wei Zhang, Lu Zhang and Zhong-Sheng Wang
Physical Chemistry Chemical Physics 2014 - vol. 16(Issue 16) pp:NaN7338-7338
Publication Date(Web):2014/03/04
DOI:10.1039/C4CP00628C
To minimize the charge recombination between electrons and the electron acceptor in solid-state dye-sensitized solar cells, we propose a separated electron donor and acceptor of a redox couple in the photoanode and in the cathode, respectively. Owing to the absence of the acceptor in the photoanode initially, the charge recombination rate is retarded remarkably, resulting in an increase of the short-circuit photocurrent by >2-fold, open-circuit photovoltage by 71 mV and power conversion efficiency by >2.5-fold.
Co-reporter:Gang Wang, Hong Sun, Lu Ding, Gang Zhou and Zhong-Sheng Wang
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 37) pp:NaN24369-24369
Publication Date(Web):2015/08/24
DOI:10.1039/C5CP03748D
A simple and versatile hydrothermal method is developed to synthesize Cu–Cu2O, in which Cu particles grow on the surface of a Cu2O truncated octahedron. Through the reduction of Cu2+ by glucose in an alkaline solution, the Cu2O truncated octahedron is quickly formed via a kinetic control process, and then Cu particles selectively nucleate on the high-energy (110) facets of Cu2O, generating a heterostructure. The amount of Cu in the sample is successfully tuned by varying the reaction temperature. Compared to Cu2O, the hybrid Cu–Cu2O architecture shows superior electrocatalytic performance for glucose oxidation due to the synergistic effect between more electrocatalytic active but less conductive Cu2O and more conductive but less electrocatalytic active Cu. By tuning the content of Cu in the heterostructure, the highest electrocatalytic activity is achieved at the Cu/Cu2O molar ratio of 0.83.
Co-reporter:Feng Gong, Zhuoqun Li, Hong Wang and Zhong-Sheng Wang
Journal of Materials Chemistry A 2012 - vol. 22(Issue 33) pp:NaN17327-17327
Publication Date(Web):2012/07/04
DOI:10.1039/C2JM33483F
Close-packed graphene suffers from a low surface area, which limits its electrocatalytic activity as the counter electrode in dye-sensitized solar cells (DSSCs). We report herein the synthesis of a porous graphene/SiO2 nanocomposite converted from graphene oxide mixed with SiO2 nanoparticles (∼12 nm) through facile hydrazine hydrate reduction. Graphene and graphene/SiO2 films prepared by drop-casting the suspensions without organic binder or surfactant onto the conductive glass substrates at room temperature without heat treatment have been applied directly as counter electrodes in DSSCs. As compared to the nonporous graphene film, the porous graphene/SiO2 composite film demonstrates much better electrocatalytic performance for the reduction of triiodide in DSSCs due to the remarkably enhanced surface area. As a consequence, the incorporation of SiO2 nanoparticles in the graphene film improves the fill factor and power conversion efficiency by 65% and 69%, respectively. With a 2.5 μm-thick graphene/SiO2 composite film as the counter electrode, the power conversion efficiency of the DSSC achieves 6.82%, which is comparable to that for the DSSC with a Pt counter electrode.
Co-reporter:Yan Li, Quanyou Feng, Hong Wang, Gang Zhou and Zhong-Sheng Wang
Journal of Materials Chemistry A 2013 - vol. 1(Issue 21) pp:NaN6349-6349
Publication Date(Web):2013/03/21
DOI:10.1039/C3TA10520B
Polypyridine complexes of Co(II)/Co(III) coupled with donor–π bridge–acceptor structured organic dyes are by far the most promising route to boost the efficiency of dye-sensitized solar cells (DSSCs). We report herein the first investigation of Ta3N5 nanorods incorporated on reduced graphene oxide (RGO) sheets as a counter electrode for application in Co(bpy)33+/2+ (bpy = 2,2′-bipyridine) mediated DSSCs. RGO–Ta3N5 composite was fabricated by mixing graphene oxide (GO) with pre-synthesized Ta3N5 nanorods (aspect ratio of ∼3) followed by facile hydrazine hydrate reduction. The composite film on conductive glass was prepared by a drop-casting process at room temperature without heat treatment. Compared with a Pt cathode with a power conversion efficiency of 7.59%, RGO–Ta3N5 exhibited comparable electrocatalytic performance for the reduction of Co(bpy)33+ species and better electrocatalytic stability in Co(bpy)33+/2+ acetonitrile solution, which was attributed to the synergetic catalytic effect of RGO and Ta3N5 nanorods and the high electrical conductivity derived from the RGO network, resulting in a power conversion efficiency of 7.85%. The present result is expected to lead to a family of composites for highly efficient cathode materials.
Co-reporter:Hong Wang, Quanyou Feng, Feng Gong, Yan Li, Gang Zhou and Zhong-Sheng Wang
Journal of Materials Chemistry A 2013 - vol. 1(Issue 1) pp:NaN104-104
Publication Date(Web):2012/11/05
DOI:10.1039/C2TA00705C
To improve the electrocatalytic performance of polyaniline thin films, an oriented polyaniline nanowires array has been successfully grown in situ on conductive glass substrates without templates and applied as the cathode of dye-sensitized solar cells (DSSCs) mediated with a Co(bpy)33+/2+ (bpy = 2,2′-bipyridine) redox couple. Compared to the polyaniline film with a random network, the oriented polyaniline nanowires array exhibits much better electrocatalytic performance, and even outperforms the typical Pt electrode in both electrocatalytic performance and electrochemical stability when exposed to the acetonitrile solution of the Co(bpy)33+/2+ redox couple. Owing to the higher electrocatalytic performance, the DSSC with the oriented nanowires array produces a higher short-circuit photocurrent and fill factor than the DSSCs with the random polyaniline network or Pt cathodes. Consequently, the power conversion efficiency of DSSCs based on a typical D–π–A organic dye sensitizer increases from 5.97% for the polyaniline random network cathode to 8.24% for the oriented polyaniline nanowires array cathode, which is also higher than the efficiency (6.78%) of the DSSC with the Pt cathode.
Co-reporter:Hong Sun, Lu Zhang and Zhong-Sheng Wang
Journal of Materials Chemistry A 2014 - vol. 2(Issue 38) pp:NaN16029-16029
Publication Date(Web):2014/07/30
DOI:10.1039/C4TA02238F
Single-crystal CoSe2 nanorods have been prepared by a facile one-step hydrothermal method. The thin CoSe2 films fabricated by drop-casting the CoSe2 nanorod suspension onto conductive substrates followed by simple drying without sintering can be used as a highly efficient electrocatalyst for the reduction of I3−. Dye-sensitized solar cells (DSSCs) with the standard N719 dye and the single-crystal CoSe2 nanorod cathode achieve a power conversion efficiency of 10.20% under AM1.5G one-sun illumination versus 8.17% for the Pt cathode. This finding implies that single-crystal CoSe2 nanorods are promising low-cost and high-performance cathode materials for high-performance DSSCs.
Co-reporter:Yan Cui, Lu Zhang, Kai Lv, Gang Zhou and Zhong-Sheng Wang
Journal of Materials Chemistry A 2015 - vol. 3(Issue 8) pp:NaN4483-4483
Publication Date(Web):2015/01/15
DOI:10.1039/C4TA06679K
Nanoparticle chains of anatase TiO2 composed of ∼5 nm nanoparticles with a high surface area (309 m2 g−1) are prepared by slow hydrolysis of titanium tetraisopropoxide modified with glacial acetic acid at a temperature of 50 °C. These nanoparticle chains without hydrothermal treatment can be used directly to fabricate photoanodes for highly efficient dye-sensitized solar cells (DSSCs), which achieve a power conversion efficiency of 9.80% at simulated AM1.5 G illumination (100 mW cm−2). The approach presented in this study demonstrates a facile synthesis of anatase TiO2 chains for use in DSSCs, which avoid hazards arising from a hydrothermal process that is typically adopted to prepare crystalline TiO2 nanoparticles for use as the photoanode in DSSCs.
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