Co-reporter:Qinghua Li, Haiyang Li, Huaibin Shen, Fangfang Wang, Feng Zhao, Feng Li, Xugu Zhang, Danyang Li, Xiao Jin, and Weifu Sun
ACS Photonics October 18, 2017 Volume 4(Issue 10) pp:2504-2504
Publication Date(Web):September 21, 2017
DOI:10.1021/acsphotonics.7b00743
Although organometal halide perovskites have garnered enormous interest in solar cells, scarce attention has been paid to light-emitting devices using formamidinium lead halide perovskite as the emitting layer. Highly luminescent and air-stable formamidinium lead halide perovskite quantum dots using high-melting-point ligands have been synthesized. Through compositional engineering, the emission spectra are readily tunable over the entire visible spectral region of 409–817 nm. The photoluminescence of FAPbX3 nanocrystals has narrow emission line widths of 21–34 nm, high quantum yields of up to 88%, and a photoluminescence lifetime of 54.6–68.6 ns for single halide FAPbBr3, which could be stable for several months. We have demonstrated the fabrication of highly efficient formamidinium lead halide perovskite quantum dot-based green-light-emitting diodes with a moderately high luminance of 33993 cd m–2, current efficiency of 20.3 cd A–1, and moderately high maximum external quantum efficiency of 4.07%.Keywords: light-emitting diodes; perovskite quantum dot; quantum yields; solid ligands; solution processing;
Co-reporter:Qinghua Li;Xiao Jin;Ying Yang;Haonan Wang;Haijiao Xu;Yuanyuan Cheng;Taihuei Wei;Yuancheng Qin;Xubiao Luo;Weifu Sun;Shenglian Luo
Advanced Functional Materials 2016 Volume 26( Issue 2) pp:254-266
Publication Date(Web):
DOI:10.1002/adfm.201503433
Novel and less toxic quantum dot (QD) semiconductors are desired for developing environmentally benign colloidal quantum dot solar cells. Here, the synthesis of novel lead/cadmium-free neodymium chalcogenide Nd2(S, Se, Te)3 QDs via solution-processed method is reported for the first time. The results show that small-bandgap semiconductor QDs with a narrow size distribution ranging from 2 to 8 nm can be produced, and the wide absorption band can be achieved by the redshift owing to the size quantization effect by controlling the initial loading of chalcogenide precursors. By analyzing the band structure of QDs and the energy level alignment between QDs and TiO2, the influence of energy offset between the conduction band edges of QDs and TiO2 on the charge transfer dynamics and photovoltaic performance of QD solar cells (QDSCs) is investigated. It is revealed that among the three types of QDs studied, Nd2Se3 QDSCs with the smallest energy offset exhibit the best performances and a decent power conversion efficiency of 3.19% is achieved. This work clearly demonstrates the promising potentials of novel rare earth chalcogenide quantum dots in photovoltaic applications.
Co-reporter:Xiao Jin, Weifu Sun, Shenglian Luo, Liping Shao, Jian Zhang, Xubiao Luo, Taihuei Wei, Yuancheng Qin, Yinglin Song and Qinghua Li
Journal of Materials Chemistry A 2015 vol. 3(Issue 47) pp:23876-23887
Publication Date(Web):19 Oct 2015
DOI:10.1039/C5TA06447C
The energy level alignment of quantum dot solar cells is key to many of the performance characteristics of devices. However, only a few of the quantum dot semiconductor systems have been available thus far, which limits the tunability of both the energy level position and absorption band edge. Here, we present a facile strategy for the first time to prepare a series of praseodymium chalcogenide colloidal quantum dots as alternate light harvesters. By sequentially layering quantum dots, rainbow quadruple-stack junctions with energy gradient architecture are constructed. It is demonstrated that the overall charge transfer time constant from the donor to the acceptor is considerably shortened from 877–1099 to 385 ps, thus leading to a significant enhancement in short-circuit current density (as high as 15.40 mA cm−2) and in power conversion efficiency by over 30% compared to its double-stack counterparts. This work reveals that the formation of the cascade energy level is desirable for robust quantum dot solar cells and concrete evidence has been provided to highlight the role of the energy level in improving photovoltaic performances such as short-circuit current density.
Co-reporter:Nan Du, Lei Ren, Weifu Sun, Xiao Jin, Qing Zhao, Yuanyuan Cheng, Taihuei Wei, Qinghua Li
Journal of Power Sources 2015 Volume 284() pp:162-169
Publication Date(Web):15 June 2015
DOI:10.1016/j.jpowsour.2015.03.041
•A binary nanofiber alloy CE-based quantum dot solar cell was prepared.•An enhanced power conversion efficiency of 3.04% is achieved.•Lower charge transfer resistance and better diffusion current density are revealed.•Red-shifts are observed for quantum dots by varying the loading of precursors.A facile, low-cost and low-temperature fabrication approach of counter electrode is essential for pursuing robust photovoltaic devices. Herein, we develop a hydrothermal in situ growth of Cobalt–Ruthenium (Co–Ru) alloy nanofiber electrode for quantum dot solar cell (QDSC) applications. Colloidal CdS QDs with tunable absorption band edge are synthesized and used as light absorber. After optimizing the QDs with the highest photoluminescence quantum yield accompanied by considerable solar light absorption ability, QDSC based on Co–Ru alloy electrode delivers a much higher power conversion efficiency than its counterparts, i.e., either pure Co or Ru metal electrodes. In detail, Co–Ru alloy electrode exhibits high specific area, excellent electrical behavior, intimate interface contact, and good stability, thus leading to notable improved device performances. The impressive robust function of Co–Ru alloy with simple manufacturing procedure highlights its potential applications in robust QDSCs.
Co-reporter:Yuancheng Qin, Yuanyuan Cheng, Longying Jiang, Xiao Jin, Mingjun Li, Xubiao Luo, Guoqing Liao, Taihuei Wei, and Qinghua Li
ACS Sustainable Chemistry & Engineering 2015 Volume 3(Issue 4) pp:637
Publication Date(Web):February 17, 2015
DOI:10.1021/sc500761n
Metal oxide nanocrystals have been pursued for various applications in photovoltaics as a buffer layer. However, it remains a challenging task to adjust their energy levels to achieve a better match of the donor–acceptor system. Herein, we report the fabrication of graphene quantum dots (GQDs) with bright blue photoluminescence by a top-down strategy based on laser fragmentation with posthydrothermal treatment. The GQDs demonstrate appropriate energy level positions and are used as an intermediate buffer layer between TiO2 and P3HT to form a cascade energy level architecture. The introduction of the GQDs into a bulk heterojunction hybrid solar cell has led to an enhancement of the power conversion efficiency.Keywords: buffer layer; carbon quantum dots; graphene; Organic/inorganic solar cells; top-down;
Co-reporter:Dongyu Li, Weifu Sun, Lexi Shao, Shuying Wu, Zhen Huang, Xiao Jin, Qin Zhang, Qinghua Li
Electrochimica Acta 2015 Volume 182() pp:416-423
Publication Date(Web):10 November 2015
DOI:10.1016/j.electacta.2015.09.023
•Up conversion nanophosphors were applied to broaden the solar light harvest.•The PCE of HSC with nanophosphor doping demonstrates a more than 30% improvement.•Photoexcited charge transfer dynamics were explored.Solar light harvesting ability is one of the key properties in organic/inorganic solar cells. One of the most popular organic materials used is poly(3-hexylthiophene) (P3HT), which can make use of solar spectrum in the range 400-600 nm, however, this polymer is incapable of utilizing low energy photons. Herein, we incorporate erbium ion decorated gadolinium oxymolybdate (GMO:Er) nanophosphors (NPs) into mesoporous acceptor film (TiO2) in an attempt to enhance the light harvest. The nanophosphor can convert the near-infrared solar spectrum to visible region (near 550 nm), in which the energy can be recaptured by P3HT. The results show that the up-conversion proceeds via the two-photon up-conversion mechanism. It is found that after the incorporation of GMO:Er NPs into TiO2 at 5 wt%, the charge transfer rate was enhanced from 2.79 to 5.83 × 109 s−1. The device performance of solar cells based on GMO:Er NPs demonstrates a more than 30% improvement compared to their neat TiO2/P3HT analogue and such enhancement can be ascribed to the broader light harvest together with faster photoexcited charge transfer. This platform can be readily implemented by introducing more demanding energy conversion phosphors and allows for the development of optoelectronic applications with tailored optoelectronic properties.Efficient bulk-heterojunction organic/inorganic hybrid solar cells achieved by tailoring solar energy spectrum and accelerating charge transfer rate.
Co-reporter:Yuancheng Qin, Xing Li, Weifu Sun, Xubiao Luo, Mingjun Li, Xinghua Tang, Xiao Jin, Yu Xie, Xinhua Ouyang and Qinghua Li
RSC Advances 2015 vol. 5(Issue 3) pp:2147-2154
Publication Date(Web):25 Nov 2014
DOI:10.1039/C4RA12188K
Two low band-gap naphthalene diimide (NDI)-based conjugated polymers have been designed and grafted with benzo[1,2-b:4,5-b′]dithiophene (BDT) or dithieno [3,2-b:2′,3′-d]pyrrole (DTP) by a Stille cross-coupling reaction. Inorganic–organic hybrid solar cells (HSCs) based on the copolymers deliver high performances by suitable molecular design and careful selection of chemical structures with different electronic nature. The well designed copolymers exhibit broader solar light absorption, which is attributed to their smaller band gaps. Density functional theory calculations and cyclic voltammetry characteristics reveal that the copolymers have small band gaps and deep HOMO and LUMO energy levels. Moreover, after introducing the copolymers, the energy level formation of the bulk-heterojunction become more matched, thus giving rise to excellent photovoltaic performances as HSCs. The results showed that an NDI-based copolymer with DTP donor segments exhibits a higher power conversion efficiency of 2.36%. This work highlights the development of bipolar host materials with a focus on molecular design strategies, which benefits the light harvest and enhances the efficiency by well aligned energy level formation.
Co-reporter:Xiao Jin, Weifu Sun, Zihan Chen, Taihuei Wei, Chuyang Chen, Xingdao He, Yongbiao Yuan, Yue Li, and Qinghua Li
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 11) pp:8771
Publication Date(Web):May 16, 2014
DOI:10.1021/am501597k
Low-temperature solution-processed photovoltaics suffer from low efficiencies because of poor exciton or electron–hole transfer. Inorganic/organic hybrid solar cell, although still in its infancy, has attracted great interest thus far. One of the promising ways to enhance exciton dissociation or electron–hole transport is the doping of lanthanide phosphate ions. However, the underlying photophysical mechanism remains poorly understood. Herein, by applying femtosecond transient absorption spectroscopy, we successfully distinguished hot electron, less energetic electron, hole transport from electron–hole recombination. Concrete evidence has been provided that lanthanide phosphate doping improves the efficiency of both hot electron and “less energetic” electron transfers from donor to acceptor, but the hole transport almost remains unchanged. In particular, the hot electron transfer lifetime was shortened from 30.2 to 12.7 ps, that is, more than 60% faster than pure TiO2 acceptor. Such improvement was ascribed to the facts that the conduction band (CB) edge energy level of TiO2 has been elevated by 0.2 eV, while the valence band level almost remains unchanged, thus not only narrowing the energy offset between CB levels of TiO2 and P3HT, but also meanwhile enlarging the band gap of TiO2 itself that permits one to inhibit electron–hole recombination within TiO2. Consequently, lanthanide phosphate doped TiO2/P3HT bulk-heterojunction solar cell has been demonstrated to be a promising hybrid solar cell, and a notable power conversion efficiency of 2.91% is therefore attained. This work indicates that lanthanide compound ions can efficiently facilitate exciton generation, dissociation, and charge transport, thus enhancing photovoltaic performance.Keywords: bulk-heterojunction; charge photogeneration dynamics; energy band regulation; inorganic/organic hybrid solar cell;
Co-reporter:Qinghua Li, Yongbiao Yuan, Zihan Chen, Xiao Jin, Tai-huei Wei, Yue Li, Yuancheng Qin, and Weifu Sun
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 15) pp:12798
Publication Date(Web):June 26, 2014
DOI:10.1021/am5027709
In this work, a core–shell nanostructure of samarium phosphates encapsulated into a Eu3+-doped silica shell has been successfully fabricated, which has been confirmed by X-ray diffraction, transmission electron microscopy (TEM), and high-resolution TEM. Moreover, we report the energy transfer process from the Sm3+ to emitters Eu3+ that widens the light absorption range of the hybrid solar cells (HSCs) and the strong enhancement of the electron-transport of TiO2/poly(3-hexylthiophene) (P3HT) bulk heterojunction (BHJ) HSCs by introducing the unique core–shell nanoarchitecture. Furthermore, by applying femtosecond transient absorption spectroscopy, we successfully obtain the electron transport lifetimes of BHJ systems with or without incorporating the core–shell nanophosphors (NPs). Concrete evidence has been provided that the doping of core–shell NPs improves the efficiency of electron transfers from donor to acceptor, but the hole transport almost remains unchanged. In particular, the hot electron transfer lifetime was shortened from 30.2 to 16.7 ps, i.e., more than 44% faster than pure TiO2 acceptor. Consequently, a notable power conversion efficiency of 3.30% for SmPO4@Eu3+:SiO2 blended TiO2/P3HT HSCs is achieved at 5 wt % as compared to 1.98% of pure TiO2/P3HT HSCs. This work indicates that the core–shell NPs can efficiently broaden the absorption region, facilitate electron-transport of BHJ, and enhance photovoltaic performance of inorganic/organic HSCs.Keywords: bulk heterojunction; charge photogeneration dynamics; core−shell nanophosphor; energy transfer; inorganic/organic hybrid solar cell
Co-reporter:Zihan Chen, Qinghua Li, Chuyang Chen, Jiaxing Du, Jifeng Tong, Xiao Jin, Yue Li, Yongbiao Yuan, Yuancheng Qin, Taihuei Wei and Weifu Sun
Physical Chemistry Chemical Physics 2014 vol. 16(Issue 44) pp:24499-24508
Publication Date(Web):02 Oct 2014
DOI:10.1039/C4CP03232B
In this work, dysprosium ion decorated yttrium oxide (Dy3+:Y2O3) nanocrystal phosphors were incorporated into TiO2 acceptor thin film in a bid to enhance the light harvest, charge separation and transfer in the hybrid solar cells. The results show that the energy level offset between the donor (P3HT) and the acceptor (Dy3+:Y2O3–TiO2) has been narrowed down, thus leading to the enhanced electron and hole transports, and also photovoltaic performances as compared to pure TiO2 without incorporating Dy3+:Y2O3. By applying femtosecond transient optical spectroscopy, after the incorporation of dopant Dy3+:Y2O3 into TiO2 at 6 wt%, both the hot electron and hole transfer lifetimes have been shortened, that is, from 30.2 ps and 6.94 ns to 25.1 ps and 1.26 ns, respectively, and an enhanced efficiency approaching 3% was achieved as compared to 2.0% without doping, indicating that the energetic charges are captured more efficiently benefitting a higher power conversion efficiency. Moreover, these results reveal that both the conduction band (CB) and valence band (VB) edges of the acceptor were elevated by 0.57 and 0.32 eV, respectively, after incorporating 6 wt% Dy3+:Y2O3. This work demonstrates that distinct energy level alignment engineered by Dy3+:Y2O3 phosphor has an important role in pursuing efficient future solar cells and underscores the promising potential of rare-earth phosphor in solar applications.
Co-reporter:Xiao Jin, Weifu Sun, Changyong Chen, Taihuei Wei, Yuanyuan Cheng, Pinjiang Li and Qinghua Li
RSC Advances 2014 vol. 4(Issue 86) pp:46008-46015
Publication Date(Web):12 Sep 2014
DOI:10.1039/C4RA08671F
Photovoltaic performances are critically dependent on efficient photoexcited charge carrier generation. Vanadium ions are introduced into titanium dioxide (TiO2) as a photocatalyst to tailor the energy level alignment of TiO2 and the conjugated polymer poly(3-hexylthiophene) (P3HT). Incorporation of vanadium ions into TiO2 yields a remarkable decrease of the energy offset between the conduction band edge of TiO2 and the lowest unoccupied molecular orbital of P3HT. The reduction of the ‘excess’ energy offset leads to a faster electron transfer at the interface of the bulk heterojunction with the lifetime decreasing from 30.2 to 19.7 ps, thus giving rise to a notable enhancement of the photovoltaic performance. That is, a power conversion efficiency of 3.01% for the vanadium-doped TiO2/P3HT solar cell at 5.0 wt% vanadium-doping is obtained as compared to 2.00% for pure TiO2.
Co-reporter:Yuancheng Qin;Xiaoxu Chen;Qunwei Tang;Benlin He;Kexin Chen;Suyue Jin;Weili Dai;Mingjun Li;Yu Xie;Yunhua Gao
Polymer Engineering & Science 2014 Volume 54( Issue 11) pp:2531-2535
Publication Date(Web):
DOI:10.1002/pen.23808
The extension of electrocatalytic reaction of I−/I3− from counter electrode/gel electrolyte interface to gel electrolyte can significantly enhance the redox kinetics and therefore conversion efficiency of dye-sensitized solar cells. Microporous gel electrolyte from polypyrrole integrated poly(hydroxyethyl methacrylate/cetytrimethylammonium bromide) [PPy-integrated poly (HEMA/CTAB)] is successfully synthesized by in-situ polymerization of pyrrole monomers in three-dimensional framework of porous poly(HEMA/CTAB) matrix. An ionic conductivity of 12.72 mS cm−1 and activation energy of 8.65 kJ mol−1 are obtained from PPy-integrated poly(HEMA/CTAB) gel electrolyte. Tafel polarization and electrochemical impedance spectroscopy are employed to characterize the electrocatalytic behaviors of the gel electrolytes. The resultant quasi-solid-state dye-sensitized solar cell shows a light-to-electrical conversion efficiency of 6.68%. POLYM. ENG. SCI., 54:2531–2535, 2014. © 2013 Society of Plastics Engineers
Co-reporter:Qinghua Li, Yongbiao Yuan, Taihuei Wei, Yue Li, Zihan Chen, Xiao Jin, Yuancheng Qin, Weifu Sun
Solar Energy Materials and Solar Cells 2014 130() pp: 426-434
Publication Date(Web):
DOI:10.1016/j.solmat.2014.07.033
Co-reporter:Weifu Sun, Zihan Chen, Junli Zhou, Dongyu Li, Zhen Huang, Xiao Jin, Qin Zhang, Feng Li and Qinghua Li
Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 48) pp:NaN33328-33328
Publication Date(Web):2016/11/10
DOI:10.1039/C6CP06571F
In this work, ytterbium–erbium co-doped strontium molybdate (SrMoO4, SMO) nanophosphors (NPs), denoted as SMO:Yb/Er, have been successfully prepared. These NPs were then incorporated into TiO2 acceptor films in hybrid solar cells to enhance light harvesting by virtue of an up-conversion process where low energy photons can be converted into high energy photons through multi-photon processes. The results showed that the SMO:Yb/Er single crystal NPs are capable of turning near infrared photons into visible ones that can be easily captured by poly(thieno[3,4-b]-thiophene/benzodithiophene) (PTB7). The results indicate that the electron transfer rate at the PTB7/TiO2 donor/acceptor interface has been boosted sharply from 0.59 to 1.35 × 109 s−1. Consequently, a hybrid solar cell based on SMO:Yb/Er NP-doped TiO2/PTB7 delivers a high power conversion efficiency of up to 3.61%, thus leading to an efficiency enhancement of around 28% as compared to that of the neat PTB7/TiO2 counterpart (2.81%). This work demonstrates a promising approach to engineering efficient photovoltaic devices by taking advantage of the versatility of rare-earth ion doped oxides that function by modifying light in the solar spectrum.
Co-reporter:Zihan Chen, Qinghua Li, Chuyang Chen, Jiaxing Du, Jifeng Tong, Xiao Jin, Yue Li, Yongbiao Yuan, Yuancheng Qin, Taihuei Wei and Weifu Sun
Physical Chemistry Chemical Physics 2014 - vol. 16(Issue 44) pp:NaN24508-24508
Publication Date(Web):2014/10/02
DOI:10.1039/C4CP03232B
In this work, dysprosium ion decorated yttrium oxide (Dy3+:Y2O3) nanocrystal phosphors were incorporated into TiO2 acceptor thin film in a bid to enhance the light harvest, charge separation and transfer in the hybrid solar cells. The results show that the energy level offset between the donor (P3HT) and the acceptor (Dy3+:Y2O3–TiO2) has been narrowed down, thus leading to the enhanced electron and hole transports, and also photovoltaic performances as compared to pure TiO2 without incorporating Dy3+:Y2O3. By applying femtosecond transient optical spectroscopy, after the incorporation of dopant Dy3+:Y2O3 into TiO2 at 6 wt%, both the hot electron and hole transfer lifetimes have been shortened, that is, from 30.2 ps and 6.94 ns to 25.1 ps and 1.26 ns, respectively, and an enhanced efficiency approaching 3% was achieved as compared to 2.0% without doping, indicating that the energetic charges are captured more efficiently benefitting a higher power conversion efficiency. Moreover, these results reveal that both the conduction band (CB) and valence band (VB) edges of the acceptor were elevated by 0.57 and 0.32 eV, respectively, after incorporating 6 wt% Dy3+:Y2O3. This work demonstrates that distinct energy level alignment engineered by Dy3+:Y2O3 phosphor has an important role in pursuing efficient future solar cells and underscores the promising potential of rare-earth phosphor in solar applications.
Co-reporter:Xiao Jin, Weifu Sun, Shenglian Luo, Liping Shao, Jian Zhang, Xubiao Luo, Taihuei Wei, Yuancheng Qin, Yinglin Song and Qinghua Li
Journal of Materials Chemistry A 2015 - vol. 3(Issue 47) pp:NaN23887-23887
Publication Date(Web):2015/10/19
DOI:10.1039/C5TA06447C
The energy level alignment of quantum dot solar cells is key to many of the performance characteristics of devices. However, only a few of the quantum dot semiconductor systems have been available thus far, which limits the tunability of both the energy level position and absorption band edge. Here, we present a facile strategy for the first time to prepare a series of praseodymium chalcogenide colloidal quantum dots as alternate light harvesters. By sequentially layering quantum dots, rainbow quadruple-stack junctions with energy gradient architecture are constructed. It is demonstrated that the overall charge transfer time constant from the donor to the acceptor is considerably shortened from 877–1099 to 385 ps, thus leading to a significant enhancement in short-circuit current density (as high as 15.40 mA cm−2) and in power conversion efficiency by over 30% compared to its double-stack counterparts. This work reveals that the formation of the cascade energy level is desirable for robust quantum dot solar cells and concrete evidence has been provided to highlight the role of the energy level in improving photovoltaic performances such as short-circuit current density.
![4H-Dithieno[3,2-b:2',3'-d]pyrrole, 4-(2-hexyldecyl)-](/data/chemimg/148300/1240405-14-4.png)
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![Benzo[1,2-b:4,5-b']dithiophene](/data/chemimg/477000/267-65-2.png)
![Benzo[1,2-b:4,5-b']dithiophene](/data/chemimg/477000/267-65-2_b.png)
