Co-reporter:Luis Lanzetta, Jose Manuel Marin-Beloqui, Irene Sanchez-Molina, Dong Ding, and Saif A. Haque
ACS Energy Letters July 14, 2017 Volume 2(Issue 7) pp:1662-1662
Publication Date(Web):June 27, 2017
DOI:10.1021/acsenergylett.7b00414
Hybrid organic lead trihalide perovskites continue to generate significant interest for use in optoelectronic devices such as solar cells and light-emitting devices. However, the toxicity of lead is considered one of the main obstacles to the commercialization of this technology. Although challenging, the replacement of lead by tin is currently the most promising alternative. Herein, we explore a class of low-dimensional, lead-free perovskite materials (2D (PEA)2SnIxBr4–x, where PEA ≡ C6H5CH2CH2NH3+) with tunable optical properties in the visible region of the spectrum. Specifically, we show that 2D (PEA)2SnI4 perovskite exhibits superior photoluminescence properties to conventional 3D CH3NH3SnI3 and that (PEA)2SnI4 can act as a sensitizer on mesoporous TiO2. We go on to demonstrate visible (∼630 nm) electroluminescence from a device employing a (PEA)2SnI4 emitter sandwiched between ITO/PEDOT:PSS and F8/LiF/Al as hole and electron injection electrodes, respectively. These devices reach a luminance of 0.15 cd/m2 at 4.7 mA/cm2 and an efficacy of 0.029 cd/A at 3.6 V. This proof-of-principle device indicates a viable path to low-dimensional, lead-free perovskite optoelectronics.
Co-reporter:Nick Aristidou;Christopher Eames;M. Saiful Islam
Journal of Materials Chemistry A 2017 vol. 5(Issue 48) pp:25469-25475
Publication Date(Web):2017/12/12
DOI:10.1039/C7TA06841G
Halide perovskites offer low cost and high efficiency solar cell materials but serious issues related to air and moisture stability remain. In this study we show, using UV-vis, fluorescence and time of flight secondary ion mass spectrometry (ToF-SIMS) techniques, that the degradation of methylammonium lead iodide solar cells is significantly accelerated when both air and moisture are present in comparison to when just air or moisture is present alone. Using ab initio computational techniques we identify the thermodynamic driving force for the enhanced reactivity and highlight the regions of the photoexcited material that are the most likely reaction centres. We suggest that water catalyses the reaction by stabilising the reactive superoxide species, enabling them to react with the methylammonium cation.
Co-reporter:Daniel Bryant, Nicholas Aristidou, Sebastian Pont, Irene Sanchez-Molina, Thana Chotchunangatchaval, Scot Wheeler, James R. Durrant and Saif A. Haque
Energy & Environmental Science 2016 vol. 9(Issue 5) pp:1655-1660
Publication Date(Web):13 Apr 2016
DOI:10.1039/C6EE00409A
Here, we demonstrate that light and oxygen-induced degradation is the main reason for the low operational stability of methylammonium lead triiodide (MeNH3PbI3) perovskite solar cells exposed to ambient conditions. When exposed to both light and dry air, unencapsulated MeNH3PbI3 solar cells rapidly degrade on timescales of minutes to a few hours. This rapid degradation is also observed under electrically bias driven current flow in the dark in the presence of O2. In contrast, significantly slower degradation is observed when the MeNH3PbI3 devices are exposed to moisture alone (e.g. 85% relative humidity in N2). We show that this light and oxygen induced degradation can be slowed down by the use of interlayers that are able to remove electrons from the perovskite film before they can react with oxygen to form O2−. These observations demonstrate that the operational stability of electronic and optoelectronic devices that exploit the electron transporting properties of MeNH3PbI3 will be critically dependent upon the use of suitable barrier layers and device configurations to mitigate the oxygen sensitivity of this remarkable material.
Co-reporter:Daniel Bryant, Nicholas Aristidou, Sebastian Pont, Irene Sanchez-Molina, Thana Chotchuangchutchaval, Scot Wheeler, James R. Durrant and Saif A. Haque
Energy & Environmental Science 2016 vol. 9(Issue 5) pp:1850-1850
Publication Date(Web):21 Apr 2016
DOI:10.1039/C6EE90023B
Correction for ‘Light and oxygen induced degradation limits the operational stability of methylammonium lead triiodide perovskite solar cells’ by Daniel Bryant et al., Energy Environ. Sci., 2016, DOI: 10.1039/c6ee00409a.
Co-reporter:Andrew J. MacLachlan;Thomas Rath;Ute B. Cappel;Simon A. Dowl;Heinz Amenitsch;Astrid-Caroline Knall;Christine Buchmaier;Gregor Trimmel;Jenny Nelson
Advanced Functional Materials 2015 Volume 25( Issue 3) pp:409-420
Publication Date(Web):
DOI:10.1002/adfm.201403108
In this work, molecular tuning of metal xanthate precursors is shown to have a marked effect on the heterojunction morphology of hybrid poly(3-hexylthiophene-2,5-diyl) (P3HT)/CdS blends and, as a result, the photochemical processes and overall performance of in situ fabricated hybrid solar cells. A series of cadmium xanthate complexes is synthesized for use as in situ precursors to cadmium sulfide nanoparticles in hybrid P3HT/CdS solar cells. The formation of CdS domains is studied by simultaneous GIWAXS (grazing incidence wide-angle X-ray scattering) and GISAXS (grazing incidence small-angle X-ray scattering), revealing knowledge about crystal growth and the formation of different morphologies observed using TEM (transmission electron microscopy). These measurements show that there is a strong relationship between precursor structure and heterojunction nanomorphology. A combination of TAS (transient absorption spectroscopy) and photovoltaic device performance measurements is used to show the intricate balance required between charge photogeneration and percolated domains in order to effectively extract charges to maximize device power conversion efficiencies. This study presents a strong case for xanthate complexes as a useful route to designing optimal heterojunction morphologies for use in the emerging field of hybrid organic/inorganic solar cells, due to the fact that the nanomorphology can be tuned via careful design of these precursor materials.
Co-reporter:Flannan T. F. O'Mahony, Yong Hui Lee, Cameron Jellett, Stoichko Dmitrov, Daniel T. J. Bryant, James R. Durrant, Brian C. O'Regan, Michael Graetzel, Mohammad K. Nazeeruddin and Saif A. Haque
Journal of Materials Chemistry A 2015 vol. 3(Issue 14) pp:7219-7223
Publication Date(Web):13 Mar 2015
DOI:10.1039/C5TA01221J
Impressive hybrid photovoltaic device performances have been realised with the methylammonium lead triiodide (MAPbI3) perovskite absorber in a wide range of device architectures. However, the question as to which of these systems represents the most commercially viable long-term prospect is yet to be answered conclusively. Here, we report on the photoinduced charge transfer processes in MAPbI3 based films measured under inert and ambient conditions. When exposed to ambient conditions, the coated mesoporous Al2O3 and bilayer systems show a rapid and significant degradation in the yield of long-lived charge separation. This process, which does not affect sensitized-mesoporous TiO2 films, is only found to occur when both light and oxygen are present. These observations indicate that the presence of a mesostructured TiO2 electron acceptor to rapidly extract the photoexcited electron from the perovskite sensitizer may be crucial for fundamental photovoltaic stability and significantly increases innate tolerance to environmental conditions. This work highlights a significant advantage of retaining mesoscale morphological control in the design of perovskite photovoltaics.
Co-reporter:T. Rath, L. Gury, I. Sánchez-Molina, L. Martínez and S. A. Haque
Chemical Communications 2015 vol. 51(Issue 50) pp:10198-10201
Publication Date(Web):27 May 2015
DOI:10.1039/C5CC03125G
Herein, we present a facile solution-based route towards nanostructured, hybrid absorber layers based on tin mono-sulfide (SnS), an emerging, non-toxic absorber material for low-cost and large-scale PV applications. Charge photogeneration properties in the hybrid system are studied using transient absorption spectroscopy and fabricated solar cells show efficient photocurrent generation over a broad spectral range.
Co-reporter:Nicholas Aristidou;Dr. Irene Sanchez-Molina;Thana Chotchuangchutchaval;Dr. Michael Brown;Dr. Luis Martinez;Dr. Thomas Rath ; Saif A. Haque
Angewandte Chemie International Edition 2015 Volume 54( Issue 28) pp:8208-8212
Publication Date(Web):
DOI:10.1002/anie.201503153
Abstract
In this paper we report on the influence of light and oxygen on the stability of CH3NH3PbI3 perovskite-based photoactive layers. When exposed to both light and dry air the mp-Al2O3/CH3NH3PbI3 photoactive layers rapidly decompose yielding methylamine, PbI2, and I2 as products. We show that this degradation is initiated by the reaction of superoxide (O2−) with the methylammonium moiety of the perovskite absorber. Fluorescent molecular probe studies indicate that the O2− species is generated by the reaction of photoexcited electrons in the perovskite and molecular oxygen. We show that the yield of O2− generation is significantly reduced when the mp-Al2O3 film is replaced with an mp-TiO2 electron extraction and transport layer. The present findings suggest that replacing the methylammonium component in CH3NH3PbI3 to a species without acid protons could improve tolerance to oxygen and enhance stability.
Co-reporter:Nicholas Aristidou;Dr. Irene Sanchez-Molina;Thana Chotchuangchutchaval;Dr. Michael Brown;Dr. Luis Martinez;Dr. Thomas Rath ; Saif A. Haque
Angewandte Chemie 2015 Volume 127( Issue 28) pp:8326-8330
Publication Date(Web):
DOI:10.1002/ange.201503153
Abstract
In this paper we report on the influence of light and oxygen on the stability of CH3NH3PbI3 perovskite-based photoactive layers. When exposed to both light and dry air the mp-Al2O3/CH3NH3PbI3 photoactive layers rapidly decompose yielding methylamine, PbI2, and I2 as products. We show that this degradation is initiated by the reaction of superoxide (O2−) with the methylammonium moiety of the perovskite absorber. Fluorescent molecular probe studies indicate that the O2− species is generated by the reaction of photoexcited electrons in the perovskite and molecular oxygen. We show that the yield of O2− generation is significantly reduced when the mp-Al2O3 film is replaced with an mp-TiO2 electron extraction and transport layer. The present findings suggest that replacing the methylammonium component in CH3NH3PbI3 to a species without acid protons could improve tolerance to oxygen and enhance stability.
Co-reporter:Rebecka Lindblad, Ute B. Cappel, Flannan T. F. O'Mahony, Hans Siegbahn, Erik M. J. Johansson, Saif A. Haque and Håkan Rensmo
Physical Chemistry Chemical Physics 2014 vol. 16(Issue 32) pp:17099-17107
Publication Date(Web):01 Jul 2014
DOI:10.1039/C4CP01581A
Semiconductor sensitized solar cell interfaces have been studied with photoelectron spectroscopy to understand the interfacial electronic structures. In particular, the experimental energy level alignment has been determined for complete TiO2/metal sulfide/polymer interfaces. For the metal sulfides CdS, Sb2S3 and Bi2S3 deposited from single source metal xanthate precursors, it was shown that both driving forces for electron injection into TiO2 and hole transfer to the polymer decrease for narrower bandgaps. The energy level alignment results were used in the discussion of the function of solar cells with the same metal sulfides as light absorbers. For example Sb2S3 showed the most favourable energy level alignment with 0.3 eV driving force for electron injection and 0.4 eV driving force for hole transfer and also the most efficient solar cells due to high photocurrent generation. The energy level alignment of the TiO2/Bi2S3 interface on the other hand showed no driving force for electron injection to TiO2, and the performance of the corresponding solar cell was very low.
Co-reporter:Andrew J. MacLachlan;Flannan T. F. O'Mahony;Anna L. Sudlow; Michael S. Hill; Kieran C. Molloy; Jenny Nelson;Dr. Saif A. Haque
ChemPhysChem 2014 Volume 15( Issue 6) pp:1019-1023
Publication Date(Web):
DOI:10.1002/cphc.201301103
Abstract
The fabrication of solution-processed nontoxic mesoporous Bi2S3 structures is demonstrated and the suitability of these structures for use in hybrid solar cells investigated. Mesoporous Bi2S3 electrodes are prepared via thermal decomposition of a thin film composed of a bismuth xanthate single source precursor. The resultant Bi2S3 films are made up of regular needles with approximate dimensions of 50×500 nm, as confirmed by scanning electron microscopy (SEM). The crystallinity of the Bi2S3 is found to be dependent on the annealing temperature, as determined by X-ray diffraction. The porous Bi2S3 films are infiltrated with the hole conductor P3HT to generate novel hybrid films, and laser-based transient absorption spectroscopy is used to interrogate the charge-separation reaction at the resulting Bi2S3/P3HT heterojunction. Specifically, optical excitation of the hybrid films results in efficient and long-lived charge separation (microsecond to millisecond timescale), thereby rendering such films suitable for the development of novel low-cost solar-energy conversion devices.
Co-reporter:Neha Bansal;Flannan T. F. O'Mahony;Thierry Lutz
Advanced Energy Materials 2013 Volume 3( Issue 8) pp:986-990
Publication Date(Web):
DOI:10.1002/aenm.201300017
Co-reporter:Simon A. Dowland, Luke X. Reynolds, Andrew MacLachlan, Ute B. Cappel and Saif A. Haque
Journal of Materials Chemistry A 2013 vol. 1(Issue 44) pp:13896-13901
Publication Date(Web):10 Oct 2013
DOI:10.1039/C3TA12962D
The influence of morphology on the photophysical properties of blend films containing in situ grown CdS and poly(3-hexylthiophene-2,5-diyl) (P3HT), fabricated utilising a metal xanthate single source precursor, is reported. A combination of transient absorption spectroscopy (TAS), transmission electron microscopy (TEM) and photovoltaic device measurements are employed to study the relationship between the efficiency of charge separation, photocurrent generation and thin film morphology. We identify that a significant proportion of the extractable charge originates from the direct excitation of CdS followed by hole-transfer to the P3HT polymer. The yield of this hole-transfer step from the inorganic CdS to the organic polymer is largely unaffected by the film's nanomorphology, while the dissociation of P3HT excitons into free charges at the CdS:P3HT interface is found to be strongly dependent on this parameter with high yields of charge transfer only being achieved at high CdS loadings. The present study elucidates design rules for the optimization of hybrid inorganic–organic solar energy conversion devices.
Co-reporter:Miquel Planells, Luke X. Reynolds, Umesh Bansode, Shraddha Chhatre, Satishchandra Ogale, Neil Robertson and Saif A. Haque
Physical Chemistry Chemical Physics 2013 vol. 15(Issue 20) pp:7679-7684
Publication Date(Web):17 Apr 2013
DOI:10.1039/C3CP50980J
We report the synthesis and optical characterisation of different triphenylamine-based hole capture materials able to anchor to CdSe quantum dots (QDs). Cyclic voltammetry studies indicate that these materials exhibit reversible electrochemical behaviour. Photoluminescence and transient absorption spectroscopy techniques are used to study interfacial charge transfer properties of the triphenylamine functionalized CdSe QDs. Specifically, we show that the functionalized QDs based on the most easily oxidised triphenylamine display efficient hole-extraction and long-lived charge separation. The present findings should help identify new strategies to control charge transfer QD-based optoelectronic devices.
Co-reporter:Flannan T. F. O'Mahony;Dr. Ute B. Cappel;Dr. Nurlan Tokmoldin;Dr. Thierry Lutz;Rebecka Lindblad; Håkan Rensmo;Dr. Saif A. Haque
Angewandte Chemie International Edition 2013 Volume 52( Issue 46) pp:12047-12051
Publication Date(Web):
DOI:10.1002/anie.201305276
Co-reporter:Flannan T. F. O'Mahony;Dr. Ute B. Cappel;Dr. Nurlan Tokmoldin;Dr. Thierry Lutz;Rebecka Lindblad; Håkan Rensmo;Dr. Saif A. Haque
Angewandte Chemie 2013 Volume 125( Issue 46) pp:12269-12273
Publication Date(Web):
DOI:10.1002/ange.201305276
Co-reporter:Ute B. Cappel, Simon A. Dowland, Luke X. Reynolds, Stoichko Dimitrov, and Saif A. Haque
The Journal of Physical Chemistry Letters 2013 Volume 4(Issue 24) pp:4253-4257
Publication Date(Web):December 2, 2013
DOI:10.1021/jz402382e
Development of design rules for hybrid inorganic–organic solar cells through understanding charge generation and recombination dynamics is an important pathway for the improvement of solar cell conversion efficiencies. In this Letter, we study the dynamics of charge generation in CdS:polymer blends by transient absorption spectroscopy. We show that charge generation following excitation of the inorganic component is highly efficient and can occur up to a few nanoseconds after excitation, allowing for diffusion of charges within the inorganic component to an interface. In contrast, charge generation following excitation of the organic component occurs on subpicosecond time scales but suffers from two loss processes, incomplete exciton dissociation and geminate recombination.Keywords: cadmium xanthate; electron transfer; hole transfer; photovoltaics; transient absorption spectroscopy;
Co-reporter:A. Bruno ; L. X. Reynolds ; C. Dyer-Smith ; J. Nelson ;S. A. Haque
The Journal of Physical Chemistry C 2013 Volume 117(Issue 39) pp:19832-19838
Publication Date(Web):September 24, 2013
DOI:10.1021/jp404985q
Emission quenching is studied in systems composed of [9,9-dioctylfluorene-co-N-(4-butylphenyl)-diphenylamine] (TFB) and various concentrations of three different types of acceptors: [6,6]-phenyl-C61 butyric acid methyl ester (mono-PCBM) and its multiadduct analogues bis-PCBM and tris-PCBM. We find that the degree of emission quenching for a given fullerene concentration decreases as the PCBM adduct number increases, while the microstructure, as observed with transmission electron microscopy, becomes more coarse. These observations are rationalized in terms of possible differences in the miscibility of fullerenes in the polymer and different excitation dissociation rates. We also extract a value for the exciton diffusion length in TFB of 9.0 ± 2 nm from ultrafast fluorescence decay measurements. The results have been confirmed with independent measurements.
Co-reporter:Flannan T. F. O'Mahony, Thierry Lutz, Néstor Guijarro, Roberto Gómez and Saif A. Haque
Energy & Environmental Science 2012 vol. 5(Issue 12) pp:9760-9764
Publication Date(Web):30 Oct 2012
DOI:10.1039/C2EE23037B
Antimony sulfide has recently demonstrated huge potential as an absorber material in solid-state semiconductor-sensitised solar cells (SSSCs). Here, we present a transient absorption spectroscopy study of the TiO2/Sb2S3/spiro-OMeTAD heterojunctions to elucidate the key factors influencing charge photogeneration. Efficient device performance requires that photoresponse extends into the near-infrared, yet we find that the efficiency of charge separation at the TiO2/Sb2S3 interface decreases significantly as increasingly red-absorbing Sb2S3 nanocrystals are photoexcited. However, the efficiency of hole transfer to spiro-OMeTAD appears much less sensitive to shifts in the Sb2S3 absorption edge and we also observe hole transfer to spiro-OMeTAD occurring on ZrO2 substrates, where electron injection does not occur. These observations may point to the importance of the hole transfer reaction not simply as a means of regenerating the sensitiser, but rather as an integral part of the charge separation process in Sb2S3 SSSCs. The present findings should help inform strategies aimed at further increasing the efficiency of nanocrystal sensitized solar cells.
Co-reporter:Luke X. Reynolds, Thierry Lutz, Simon Dowland, Andrew MacLachlan, Simon King and Saif A. Haque
Nanoscale 2012 vol. 4(Issue 5) pp:1561-1564
Publication Date(Web):06 Feb 2012
DOI:10.1039/C2NR12081J
We demonstrate that blend films containing poly(3-hexylthiophene-2,5-diyl) and in situ grown CdS display a greater yield of photogenerated charges than a blend containing an equivalent amount of pre-synthesised CdS quantum dots. Moreover, we show that the greater charge yield in the in situ grown films leads to an improvement in device efficiency. The present findings also appear to suggest that charge photogeneration at the CdS/polymer heterojunction is facilitated by the formation of nanoparticle networks as a result of CdS aggregation.
Co-reporter:Thierry Lutz, Andrew MacLachlan, Anna Sudlow, Jenny Nelson, Michael S. Hill, Kieran C. Molloy and Saif A. Haque
Physical Chemistry Chemical Physics 2012 vol. 14(Issue 47) pp:16192-16196
Publication Date(Web):06 Nov 2012
DOI:10.1039/C2CP43534A
We introduce a straightforward route to the fabrication of metal sulfide semiconductor (e.g. CdS, Sb2S3, Bi2S3) sensitised TiO2 films. Our approach is based upon the controllable thermal decomposition of a single-source metal xanthate precursor on a mesoporous metal oxide film. The growth of the metal sulfide deposit is confirmed by Raman and UV-Vis steady-state absorption measurements. Transient absorption spectroscopy measurements provide evidence for charge separation across the metal sulfide/TiO2 interface. Moreover, a high yield of long-lived photogenerated charges is observed in a three-component TiO2/metal sulfide/spiro-OMeTAD film, thus demonstrating the potential of such multicomponent films for solar energy conversion devices.
Co-reporter:Anne A. Y. Guilbert, Luke X. Reynolds, Annalisa Bruno, Andrew MacLachlan, Simon P. King, Mark A. Faist, Ellis Pires, J. Emyr Macdonald, Natalie Stingelin, Saif A. Haque, and Jenny Nelson
ACS Nano 2012 Volume 6(Issue 5) pp:3868
Publication Date(Web):April 25, 2012
DOI:10.1021/nn204996w
The bis and tris adducts of [6,6]phenyl-C61-butyric acid methyl ester (PCBM) offer lower reduction potentials than PCBM and are therefore expected to offer larger open-circuit voltages and more efficient energy conversion when blended with conjugated polymers in photovoltaic devices in place of PCBM. However, poor photovoltaic device performances are commonly observed when PCBM is replaced with higher-adduct fullerenes. In this work, we use transmission electron microscopy (TEM), steady-state and ultrafast time-resolved photoluminescence spectroscopy (PL), and differential scanning calorimetry (DSC) to probe the microstructural properties of blend films of poly(3-hexylthiophene-2,5-diyl) (P3HT) with the bis and tris adducts of PCBM. TEM and PL indicate that, in as-spun blend films, fullerenes become less soluble in P3HT as the number of adducts increases. PL indicates that upon annealing crystallization leads to phase separation in P3HT:PCBM samples only. DSC studies indicate that the interactions between P3HT and the fullerene become weaker with higher-adduct fullerenes and that all systems exhibit eutectic phase behavior with a eutectic composition being shifted to higher molar fullerene content for higher-adduct fullerenes. We propose two different mechanisms of microstructure development for PCBM and higher-adduct fullerenes. P3HT:PCBM blends, phase segregation is the result of crystallization of either one or both components and is facilitated by thermal treatments. In contrast, for blends containing higher adducts, the phase separation is due to a partial demixing of the amorphous phases. We rationalize the lower photocurrent generation by the higher-adduct fullerene blends in terms of film microstructure.Keywords: DSC; fullerenes; microstructure; organic solar cells; phase behavior; PL; TEM
Co-reporter:Néstor Guijarro, Thierry Lutz, Teresa Lana-Villarreal, Flannan O’Mahony, Roberto Gómez, and Saif A. Haque
The Journal of Physical Chemistry Letters 2012 Volume 3(Issue 10) pp:1351-1356
Publication Date(Web):May 7, 2012
DOI:10.1021/jz3004365
Photovoltaic devices comprising metal chalcogenide nanocrystals as light-harvesting components are emerging as a promising power-generation technology. Here, we report a strategy to evenly deposit Sb2Se3 nanoparticles on mesoporous TiO2 as confirmed by Raman spectroscopy, energy-dispersive X-ray spectrometry, and transmission electron microscopy. Detailed study of the interfacial charge transfer dynamics by means of transient absorption spectroscopy provides evidence of electron injection across the Sb2Se3/TiO2 interface upon illumination, which can be improved 3-fold by annealing at low temperatures. Following addition of the spiro-OMeTAD hole transporting material, regeneration yields exceeding 80% are achieved, and the lifetime of the charge separated species is found to be on the millisecond time scale (τ50% ∼ 50 ms). These findings are discussed with respect to the design of solid-state Sb2Se3 sensitized solar cells.Keywords: charge separation; dye-sensitized solar cells; nanoparticles; quantum dot; SILAR; solar cell; transient absorption spectroscopy;
Co-reporter:Simon Dowl;Thierry Lutz;Alexer Ward;Simon P. King;Anna Sudlow;Michael S. Hill;Kieran C. Molloy
Advanced Materials 2011 Volume 23( Issue 24) pp:2739-2744
Publication Date(Web):
DOI:10.1002/adma.201100625
Co-reporter:Henry C. Leventis, Simon P. King, Anna Sudlow, Michael S. Hill, Kieran C. Molloy and Saif A. Haque
Nano Letters 2010 Volume 10(Issue 4) pp:1253-1258
Publication Date(Web):March 12, 2010
DOI:10.1021/nl903787j
Nanostructured composites of inorganic and organic materials are attracting extensive interest for electronic and optoelectronic device applications. In this paper, we introduce a general method for the fabrication of metal sulfide nanoparticle/polymer films employing a low-cost and low temperature route compatible with large-scale device manufacturing. Our approach is based upon the controlled in situ thermal decomposition of a solution processable metal xanthate precursor complex in a semiconducting polymer film. To demonstrate the versatility of our method, we fabricate a CdS/P3HT nanocomposite film and show that the metal sulfide network inside the polymer film assists in the absorption of visible light and enables the achievement of high yields of charge photogeneration at the CdS/P3HT heterojunction. Photovoltaic devices based upon such nanocomposite films show solar light to electrical energy conversion efficiencies of 0.7% under full AM1.5 illumination and 1.2% under 10% incident power, demonstrating the potential of such nanocomposite films for low-cost photovoltaic devices.
Co-reporter:Henry C. Leventis ; Flannan O’Mahony ; Javeed Akhtar ; Mohammad Afzaal ; Paul O’Brien
Journal of the American Chemical Society 2010 Volume 132(Issue 8) pp:2743-2750
Publication Date(Web):February 3, 2010
DOI:10.1021/ja909172p
We report a transient absorption and luminescence study addressing the charge separation, recombination, and regeneration reactions at nanostructured metal oxide/PbS quantum dot/organic hole conductor heterojunctions. We show that yields of charge separation are significantly higher at PbS/SnO2 interfaces relative to PbS/TiO2 interfaces, and conclude that this behavior is a result of the ca. 300−500 meV lower conduction band edge in SnO2 as compared to TiO2. We also report a correlation between the PbS particle size and the yield of charge separation at PbS/SnO2 interfaces, with a smaller PbS particle radius resulting a higher yield of charge separation. Finally we investigated the regeneration of the photooxidized PbS by an organic hole transporting material, namely, spiro-OMeTAD. The overall spiro-OMeTAD+ yield is found to be 27% at a SnO2/PbS (∼3 nm diameter)/spiro-OMeTAD heterojunction. The addition of a lithium salt was found to raise the overall spiro-OMeTAD+ yield from its initial value of 27% (where no Li+ is present) to 50%. We believe this to be a result of an increase in the primary charge injection yield to near unity as the SnO2 conduction band is lowered (with increasing [Li+]), increasing the driving force for electron injection. The present findings are discussed with relevance to the design of PbS-sensitized metal oxide layers for DSSCs.
Co-reporter:Henry C. Leventis and Saif A. Haque
Energy & Environmental Science 2009 vol. 2(Issue 11) pp:1176-1179
Publication Date(Web):05 Aug 2009
DOI:10.1039/B911527G
A hybrid dye/CdS-sensitized TiO2 solar cell architecture is presented whereby the CdS nanocrystal layer is shown to perform multiple functions—retarding interfacial charge recombination and harvesting short-wavelength light, whilst acting as a redox mediator in the injection of electrons from the photo-excited dye into the mesoporous TiO2nanoparticle film.
Co-reporter:Nurlan Tokmoldin;Nicholas Griffiths;Donal D. C. Bradley
Advanced Materials 2009 Volume 21( Issue 34) pp:3475-3478
Publication Date(Web):
DOI:10.1002/adma.200802594
Co-reporter:Simon King, Michael Sommer, Sven Huettner, Mukundan Thelakkat and Saif A. Haque
Journal of Materials Chemistry A 2009 vol. 19(Issue 30) pp:5436-5441
Publication Date(Web):29 Jun 2009
DOI:10.1039/B905708K
A series of donor–acceptor diblock copolymers with varying molecular weight are studied in thin film and compared with an ‘equivalent’ blend formed from donor and acceptor homopolymers. Steady-state and transient spectroscopies are used to demonstrate a correlation between low molecular weight block copolymers and increased photoluminescence quenching (up to 99%) leading to higher yields of long-lived free charges. Such block copolymers are shown, by electron microscopy, to exhibit phase-segregated micrdomains whose size and periodicity are determined by their molecular weight. Photovoltaic devices made using these materials show a peak efficiency of 0.11% and correlate with our spectroscopic results, subject to a trade-off between charge generation and tranpsort/collection.
Co-reporter:J. Huang;N. Tokmoldin;S. A. Haque;S. Koops;J. R. Durrant;E. Palomares;D. D. C. Bradley
Advanced Materials 2007 Volume 19(Issue 5) pp:683-687
Publication Date(Web):5 FEB 2007
DOI:10.1002/adma.200601619
A light-emitting diode based upon a three-component hybrid inorganic/organic nanocomposite film, comprising a mesoporous TiO2 film, a light-emitting polymer adsorbed to the metal-oxide surface, and a hole-transporting polymer interpenetrated into the film pores (see figure), is described: it allows the luminescence and charge-carrier transport processes to be tuned individually.
Co-reporter:Samantha Handa, Helga Wietasch, Mukundan Thelakkat, James R. Durrant and Saif A. Haque
Chemical Communications 2007 (Issue 17) pp:1725-1727
Publication Date(Web):03 Apr 2007
DOI:10.1039/B618700E
Herein we report the application of supramolecular dyes to control charge recombination between photo-injected electrons and oxidized hole-transporting material, resulting in an enhancement in the performance of dye sensitized solar cell devices based upon such dyes.
Co-reporter:Saif A. Haque Dr.;Samantha Ha;Katja Peter;Emilio Palomares Dr.;Mukundan Thelakkat Dr.;James R. Durrant Dr.
Angewandte Chemie International Edition 2005 Volume 44(Issue 35) pp:
Publication Date(Web):1 AUG 2005
DOI:10.1002/anie.200500363
A trial separation: A dye-sensitized nanocrystalline TiO2 film (see scheme) is prepared in which a remarkably long-lived (4 s) charge-separated state can be generated. The key parameter that controls charge transfer at the dye/TiO2 interface is shown to be the spatial separation between the cation center of the dye and the electrode surface.
Co-reporter:Saif A. Haque Dr.;Samantha Ha;Katja Peter;Emilio Palomares Dr.;Mukundan Thelakkat Dr.;James R. Durrant Dr.
Angewandte Chemie 2005 Volume 117(Issue 35) pp:
Publication Date(Web):1 AUG 2005
DOI:10.1002/ange.200500363
Trennung auf Zeit: In einem Farbstoff-sensibilisierten nanokristallinen TiO2-Film (siehe Schema) kann ein bemerkenswert langlebiger (4 s) ladungsgetrennter Zustand erzeugt werden. Als Schlüsselparameter für die Steuerung des Ladungstransfers an der Farbstoff/TiO2-Grenzfläche erwies sich der Abstand zwischen dem Kationenzentrum des Farbstoffs und der Elektrodenoberfläche.
Co-reporter:S. A. Haque;J. S. Park;M. Srinivasarao;J. R. Durrant
Advanced Materials 2004 Volume 16(Issue 14) pp:
Publication Date(Web):2 AUG 2004
DOI:10.1002/adma.200400327
A novel approach to the attachment of molecular dyes to nanocrystalline TiO2 electrodes (see Figure) is reported. Cyclodextrin encapsulation of an organic dye is shown to result in strong binding to the metal oxide electrode. The encapsulation furthermore results in a well-defined spatial separation of the organic dye from the electrode surface, allowing the photogeneration of a long-lived charge-separated state.
Co-reporter:Simon King, Michael Sommer, Sven Huettner, Mukundan Thelakkat and Saif A. Haque
Journal of Materials Chemistry A 2009 - vol. 19(Issue 30) pp:NaN5441-5441
Publication Date(Web):2009/06/29
DOI:10.1039/B905708K
A series of donor–acceptor diblock copolymers with varying molecular weight are studied in thin film and compared with an ‘equivalent’ blend formed from donor and acceptor homopolymers. Steady-state and transient spectroscopies are used to demonstrate a correlation between low molecular weight block copolymers and increased photoluminescence quenching (up to 99%) leading to higher yields of long-lived free charges. Such block copolymers are shown, by electron microscopy, to exhibit phase-segregated micrdomains whose size and periodicity are determined by their molecular weight. Photovoltaic devices made using these materials show a peak efficiency of 0.11% and correlate with our spectroscopic results, subject to a trade-off between charge generation and tranpsort/collection.
Co-reporter:Samantha Handa, Helga Wietasch, Mukundan Thelakkat, James R. Durrant and Saif A. Haque
Chemical Communications 2007(Issue 17) pp:NaN1727-1727
Publication Date(Web):2007/04/03
DOI:10.1039/B618700E
Herein we report the application of supramolecular dyes to control charge recombination between photo-injected electrons and oxidized hole-transporting material, resulting in an enhancement in the performance of dye sensitized solar cell devices based upon such dyes.
Co-reporter:Miquel Planells, Luke X. Reynolds, Umesh Bansode, Shraddha Chhatre, Satishchandra Ogale, Neil Robertson and Saif A. Haque
Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 20) pp:NaN7684-7684
Publication Date(Web):2013/04/17
DOI:10.1039/C3CP50980J
We report the synthesis and optical characterisation of different triphenylamine-based hole capture materials able to anchor to CdSe quantum dots (QDs). Cyclic voltammetry studies indicate that these materials exhibit reversible electrochemical behaviour. Photoluminescence and transient absorption spectroscopy techniques are used to study interfacial charge transfer properties of the triphenylamine functionalized CdSe QDs. Specifically, we show that the functionalized QDs based on the most easily oxidised triphenylamine display efficient hole-extraction and long-lived charge separation. The present findings should help identify new strategies to control charge transfer QD-based optoelectronic devices.
Co-reporter:Rebecka Lindblad, Ute B. Cappel, Flannan T. F. O'Mahony, Hans Siegbahn, Erik M. J. Johansson, Saif A. Haque and Håkan Rensmo
Physical Chemistry Chemical Physics 2014 - vol. 16(Issue 32) pp:NaN17107-17107
Publication Date(Web):2014/07/01
DOI:10.1039/C4CP01581A
Semiconductor sensitized solar cell interfaces have been studied with photoelectron spectroscopy to understand the interfacial electronic structures. In particular, the experimental energy level alignment has been determined for complete TiO2/metal sulfide/polymer interfaces. For the metal sulfides CdS, Sb2S3 and Bi2S3 deposited from single source metal xanthate precursors, it was shown that both driving forces for electron injection into TiO2 and hole transfer to the polymer decrease for narrower bandgaps. The energy level alignment results were used in the discussion of the function of solar cells with the same metal sulfides as light absorbers. For example Sb2S3 showed the most favourable energy level alignment with 0.3 eV driving force for electron injection and 0.4 eV driving force for hole transfer and also the most efficient solar cells due to high photocurrent generation. The energy level alignment of the TiO2/Bi2S3 interface on the other hand showed no driving force for electron injection to TiO2, and the performance of the corresponding solar cell was very low.
Co-reporter:Thierry Lutz, Andrew MacLachlan, Anna Sudlow, Jenny Nelson, Michael S. Hill, Kieran C. Molloy and Saif A. Haque
Physical Chemistry Chemical Physics 2012 - vol. 14(Issue 47) pp:NaN16196-16196
Publication Date(Web):2012/11/06
DOI:10.1039/C2CP43534A
We introduce a straightforward route to the fabrication of metal sulfide semiconductor (e.g. CdS, Sb2S3, Bi2S3) sensitised TiO2 films. Our approach is based upon the controllable thermal decomposition of a single-source metal xanthate precursor on a mesoporous metal oxide film. The growth of the metal sulfide deposit is confirmed by Raman and UV-Vis steady-state absorption measurements. Transient absorption spectroscopy measurements provide evidence for charge separation across the metal sulfide/TiO2 interface. Moreover, a high yield of long-lived photogenerated charges is observed in a three-component TiO2/metal sulfide/spiro-OMeTAD film, thus demonstrating the potential of such multicomponent films for solar energy conversion devices.
Co-reporter:T. Rath, L. Gury, I. Sánchez-Molina, L. Martínez and S. A. Haque
Chemical Communications 2015 - vol. 51(Issue 50) pp:NaN10201-10201
Publication Date(Web):2015/05/27
DOI:10.1039/C5CC03125G
Herein, we present a facile solution-based route towards nanostructured, hybrid absorber layers based on tin mono-sulfide (SnS), an emerging, non-toxic absorber material for low-cost and large-scale PV applications. Charge photogeneration properties in the hybrid system are studied using transient absorption spectroscopy and fabricated solar cells show efficient photocurrent generation over a broad spectral range.
Co-reporter:Flannan T. F. O'Mahony, Yong Hui Lee, Cameron Jellett, Stoichko Dmitrov, Daniel T. J. Bryant, James R. Durrant, Brian C. O'Regan, Michael Graetzel, Mohammad K. Nazeeruddin and Saif A. Haque
Journal of Materials Chemistry A 2015 - vol. 3(Issue 14) pp:NaN7223-7223
Publication Date(Web):2015/03/13
DOI:10.1039/C5TA01221J
Impressive hybrid photovoltaic device performances have been realised with the methylammonium lead triiodide (MAPbI3) perovskite absorber in a wide range of device architectures. However, the question as to which of these systems represents the most commercially viable long-term prospect is yet to be answered conclusively. Here, we report on the photoinduced charge transfer processes in MAPbI3 based films measured under inert and ambient conditions. When exposed to ambient conditions, the coated mesoporous Al2O3 and bilayer systems show a rapid and significant degradation in the yield of long-lived charge separation. This process, which does not affect sensitized-mesoporous TiO2 films, is only found to occur when both light and oxygen are present. These observations indicate that the presence of a mesostructured TiO2 electron acceptor to rapidly extract the photoexcited electron from the perovskite sensitizer may be crucial for fundamental photovoltaic stability and significantly increases innate tolerance to environmental conditions. This work highlights a significant advantage of retaining mesoscale morphological control in the design of perovskite photovoltaics.
Co-reporter:Simon A. Dowland, Luke X. Reynolds, Andrew MacLachlan, Ute B. Cappel and Saif A. Haque
Journal of Materials Chemistry A 2013 - vol. 1(Issue 44) pp:NaN13901-13901
Publication Date(Web):2013/10/10
DOI:10.1039/C3TA12962D
The influence of morphology on the photophysical properties of blend films containing in situ grown CdS and poly(3-hexylthiophene-2,5-diyl) (P3HT), fabricated utilising a metal xanthate single source precursor, is reported. A combination of transient absorption spectroscopy (TAS), transmission electron microscopy (TEM) and photovoltaic device measurements are employed to study the relationship between the efficiency of charge separation, photocurrent generation and thin film morphology. We identify that a significant proportion of the extractable charge originates from the direct excitation of CdS followed by hole-transfer to the P3HT polymer. The yield of this hole-transfer step from the inorganic CdS to the organic polymer is largely unaffected by the film's nanomorphology, while the dissociation of P3HT excitons into free charges at the CdS:P3HT interface is found to be strongly dependent on this parameter with high yields of charge transfer only being achieved at high CdS loadings. The present study elucidates design rules for the optimization of hybrid inorganic–organic solar energy conversion devices.
![Poly[(phenylimino)(9,9-dioctyl-9H-fluorene-2,7-diyl)(phenylimino)-1,4-ph
enylene[9,9-bis(3,6,9,12-tetraoxatridec-1-yl)-9H-fluorene-2,7-diyl]-1,4-p
henylene]](http://img.cochemist.com/ccimg/880500/880487-38-7.png)
![Poly[(phenylimino)(9,9-dioctyl-9H-fluorene-2,7-diyl)(phenylimino)-1,4-ph
enylene[9,9-bis(3,6,9,12-tetraoxatridec-1-yl)-9H-fluorene-2,7-diyl]-1,4-p
henylene]](http://img.cochemist.com/ccimg/880500/880487-38-7_b.png)
[(3,5-difl
uorophenyl)imino]-1,4-phenylene[9,9-bis(3,6,9,12-tetraoxatridec-1-yl)-9
H-fluorene-2,7-diyl]-1,4-phenylene]](http://img.cochemist.com/ccimg/880500/880487-40-1.png)
[(3,5-difl
uorophenyl)imino]-1,4-phenylene[9,9-bis(3,6,9,12-tetraoxatridec-1-yl)-9
H-fluorene-2,7-diyl]-1,4-phenylene]](http://img.cochemist.com/ccimg/880500/880487-40-1_b.png)
[(4-meth
oxyphenyl)imino]-1,4-phenylene[9,9-bis(3,6,9,12-tetraoxatridec-1-yl)-9H
-fluorene-2,7-diyl]-1,4-phenylene]](http://img.cochemist.com/ccimg/771600/771563-22-5.png)
[(4-meth
oxyphenyl)imino]-1,4-phenylene[9,9-bis(3,6,9,12-tetraoxatridec-1-yl)-9H
-fluorene-2,7-diyl]-1,4-phenylene]](http://img.cochemist.com/ccimg/771600/771563-22-5_b.png)
![Poly[[(4-butylphenyl)imino]-1,4-phenylene(9,9-dioctyl-9H-fluorene-2,7-di
yl)-1,4-phenylene]](/data/chemimg/3111200/223569-31-1.png)
![Poly[[(4-butylphenyl)imino]-1,4-phenylene(9,9-dioctyl-9H-fluorene-2,7-di
yl)-1,4-phenylene]](/data/chemimg/3111200/223569-31-1_b.png)
![Poly[[[4-(1-methylpropyl)phenyl]imino]-1,4-phenylene(9,9-dioctyl-9H-fluo
rene-2,7-diyl)-1,4-phenylene]](/data/chemimg/3109700/220797-16-0.png)
![Poly[[[4-(1-methylpropyl)phenyl]imino]-1,4-phenylene(9,9-dioctyl-9H-fluo
rene-2,7-diyl)-1,4-phenylene]](/data/chemimg/3109700/220797-16-0_b.png)
![POLY[[(4-METHYLPHENYL)IMINO][1,1'-BIPHENYL]-4,4'-DIYL[(4-METHYLPHENYL)IMINO]-1,4-PHENYLENE-1,2-ETHENEDIYL[[(2-ETHYLHEXYL)OXY]METHOXY-1,4-PHENYLENE]-1,2-ETHENEDIYL(2,5-DIMETHOXY-1,4-PHENYLENE)-1,2-ETHENEDIYL[[(2-ETHYLHEXYL)OXY]METHOXY-1,4-PHENYLENE]-1,2-ETHENEDIYL-1,4-PHENYLENE]](http://img.cochemist.com/ccimg/871300/871240-96-9.png)
![POLY[[(4-METHYLPHENYL)IMINO][1,1'-BIPHENYL]-4,4'-DIYL[(4-METHYLPHENYL)IMINO]-1,4-PHENYLENE-1,2-ETHENEDIYL[[(2-ETHYLHEXYL)OXY]METHOXY-1,4-PHENYLENE]-1,2-ETHENEDIYL(2,5-DIMETHOXY-1,4-PHENYLENE)-1,2-ETHENEDIYL[[(2-ETHYLHEXYL)OXY]METHOXY-1,4-PHENYLENE]-1,2-ETHENEDIYL-1,4-PHENYLENE]](http://img.cochemist.com/ccimg/871300/871240-96-9_b.png)
[(4-FLUOROPHENYL)IMINO]-1,4-PHENYLENE[9,9-BIS(3,6,9,12-TETRAOXATRIDEC-1-YL)-9H-FLUORENE-2,7-DIYL]-1,4-PHENYLENE]](http://img.cochemist.com/ccimg/880500/880487-39-8.png)
[(4-FLUOROPHENYL)IMINO]-1,4-PHENYLENE[9,9-BIS(3,6,9,12-TETRAOXATRIDEC-1-YL)-9H-FLUORENE-2,7-DIYL]-1,4-PHENYLENE]](http://img.cochemist.com/ccimg/880500/880487-39-8_b.png)
![[1,1'-Biphenyl]-4,4'-diamine, N,N'-bis(4-methoxyphenyl)-N,N'-diphenyl-](http://img.cochemist.com/ccimg/20500/20441-07-0.png)
![[1,1'-Biphenyl]-4,4'-diamine, N,N'-bis(4-methoxyphenyl)-N,N'-diphenyl-](http://img.cochemist.com/ccimg/20500/20441-07-0_b.png)
![4,4'-{(E)-diazene-1,2-diylbis[benzene-4,1-diyl(E)diazene-2,1-diyl]}bis(N,N-dimethylnaphthalen-1-amine)](http://img.cochemist.com/ccimg/69200/69163-06-0.png)
![4,4'-{(E)-diazene-1,2-diylbis[benzene-4,1-diyl(E)diazene-2,1-diyl]}bis(N,N-dimethylnaphthalen-1-amine)](http://img.cochemist.com/ccimg/69200/69163-06-0_b.png)
![2,2'-Bipyridine, 6-(5-[2,2'-bipyridin]-6-yl-1,1-dimethyl-3,4-diphenylsilacyclopenta-2,4-dien-2-yl)-](/data/chemimg/1202800/350042-00-1.png)
![2,2'-Bipyridine, 6-(5-[2,2'-bipyridin]-6-yl-1,1-dimethyl-3,4-diphenylsilacyclopenta-2,4-dien-2-yl)-](/data/chemimg/1202800/350042-00-1_b.png)
![Zincate(4-),[[4,4',4'',4'''-(21H,23H-porphine-5,10,15,20-tetrayl-kN21,kN22,kN23,kN24)tetrakis[benzoato]](6-)]-,hydrogen (1:4), (SP-4-1)-](/data/chemimg/27647-84-3.png)
![Zincate(4-),[[4,4',4'',4'''-(21H,23H-porphine-5,10,15,20-tetrayl-kN21,kN22,kN23,kN24)tetrakis[benzoato]](6-)]-,hydrogen (1:4), (SP-4-1)-](/data/chemimg/27647-84-3_b.png)
![Poly[[2,2'-bithiophene]-5,5'-diyl(9,9-dioctyl-9H-fluorene-2,7-diyl)]](http://img.cochemist.com/ccimg/210400/210347-56-1.png)
![Poly[[2,2'-bithiophene]-5,5'-diyl(9,9-dioctyl-9H-fluorene-2,7-diyl)]](http://img.cochemist.com/ccimg/210400/210347-56-1_b.png)
![[1,1'-Biphenyl]-4,4'-diamine, N4,N4,N4',N4'-tetrakis(4-methoxyphenyl)-](/data/chemimg/101000/122738-21-0.png)
![[1,1'-Biphenyl]-4,4'-diamine, N4,N4,N4',N4'-tetrakis(4-methoxyphenyl)-](/data/chemimg/101000/122738-21-0_b.png)
![Poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,7-diyl)]](/data/chemimg/107700/210347-52-7.png)
![Poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,7-diyl)]](/data/chemimg/107700/210347-52-7_b.png)
![N2,N2,N2',N2',N7,N7,N7',N7'-Octakis(4-methoxyphenyl)-9,9'-spirobi[fluorene]-2,2',7,7'-tetraamine](http://img.cochemist.com/ccimg/207800/207739-72-8.png)
![N2,N2,N2',N2',N7,N7,N7',N7'-Octakis(4-methoxyphenyl)-9,9'-spirobi[fluorene]-2,2',7,7'-tetraamine](http://img.cochemist.com/ccimg/207800/207739-72-8_b.png)
![Poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene]](http://img.cochemist.com/ccimg/888500/888491-19-8.png)
![Poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene]](http://img.cochemist.com/ccimg/888500/888491-19-8_b.png)
![Poly[[2-[(3,7-dimethyloctyl)oxy]-5-methoxy-1,4-phenylene]-1,2-ethenediyl]](http://img.cochemist.com/ccimg/177800/177716-59-5.png)
![Poly[[2-[(3,7-dimethyloctyl)oxy]-5-methoxy-1,4-phenylene]-1,2-ethenediyl]](http://img.cochemist.com/ccimg/177800/177716-59-5_b.png)
![Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]](http://img.cochemist.com/ccimg/138200/138184-36-8.png)
![Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]](http://img.cochemist.com/ccimg/138200/138184-36-8_b.png)
