Publications
46 results found
O'Mahony FTF, Lee YH, Jellett C, et al., 2015, Improved environmental stability of organic lead trihalide perovskite-based photoactive-layers in the presence of mesoporous TiO2, Journal of Materials Chemistry A, Vol: 3, Pages: 7219-7223, ISSN: 2050-7496
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.
Dimitrov SD, Wheeler S, Niedzialek D, et al., 2015, Polaron pair mediated triplet generation in polymer/fullerene blends, Nature Communications, Vol: 6, ISSN: 2041-1723
Electron spin is a key consideration for the function of organic semiconductors in light-emitting diodes and solar cells, as well as spintronic applications relying on organic magnetoresistance. A mechanism for triplet excited state generation in such systems is by recombination of electron-hole pairs. However, the exact charge recombination mechanism, whether geminate or nongeminate and whether it involves spin-state mixing is not well understood. In this work, the dynamics of free charge separation competing with recombination to polymer triplet states is studied in two closely related polymer-fullerene blends with differing polymer fluorination and photovoltaic performance. Using time-resolved laser spectroscopic techniques and quantum chemical calculations, we show that lower charge separation in the fluorinated system is associated with the formation of bound electron-hole pairs, which undergo spin-state mixing on the nanosecond timescale and subsequent geminate recombination to triplet excitons. We find that these bound electron-hole pairs can be dissociated by electric fields.
Law C, Miseikis L, Dimitrov S, et al., 2014, Performance and Stability of Lead Perovskite/TiO<sub>2</sub>, Polymer/PCBM, and Dye Sensitized Solar Cells at Light Intensities up to 70 Suns, ADVANCED MATERIALS, Vol: 26, Pages: 6268-6273, ISSN: 0935-9648
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- Citations: 94
Dimitrov SD, Huang Z, Deledalle F, et al., 2014, Towards optimisation of photocurrent from fullerene excitons in organic solar cells, ENERGY & ENVIRONMENTAL SCIENCE, Vol: 7, Pages: 1037-1043, ISSN: 1754-5692
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- Citations: 38
Dimitrov SD, Durrant JR, 2014, Materials Design Considerations for Charge Generation in Organic Solar Cells, CHEMISTRY OF MATERIALS, Vol: 26, Pages: 616-630, ISSN: 0897-4756
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- Citations: 221
Shivanna R, Shoaee S, Dimitrov S, et al., 2014, Charge generation and transport in efficient organic bulk heterojunction solar cells with a perylene acceptor, ENERGY & ENVIRONMENTAL SCIENCE, Vol: 7, Pages: 435-441, ISSN: 1754-5692
Huang Z, Fregoso EC, Dimitrov S, et al., 2014, Optimisation of diketopyrrolopyrrole:fullerene solar cell performance through control of polymer molecular weight and thermal annealing, JOURNAL OF MATERIALS CHEMISTRY A, Vol: 2, Pages: 19282-19289, ISSN: 2050-7488
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- Citations: 24
Cappel UB, Dowland SA, Reynolds LX, et al., 2013, Charge Generation Dynamics in CdS:P3HT Blends for Hybrid Solar Cells, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, Vol: 4, Pages: 4253-4257, ISSN: 1948-7185
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- Citations: 28
Bronstein H, Hurhangee M, Fregoso EC, et al., 2013, Isostructural, Deeper Highest Occupied Molecular Orbital Analogues of Poly(3-hexylthiophene) for High-Open Circuit Voltage Organic Solar Cells, CHEMISTRY OF MATERIALS, Vol: 25, Pages: 4239-4249, ISSN: 0897-4756
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- Citations: 53
Bakulin AA, Dimitrov SD, Rao A, et al., 2013, Charge-Transfer State Dynamics Following Hole and Electron Transfer in Organic Photovoltaic Devices, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, Vol: 4, Pages: 209-215, ISSN: 1948-7185
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- Citations: 116
Juozapavicius M, Kaucikas M, Dimitrov SD, et al., 2013, Evidence for “Slow” Electron Injection in Commercially Relevant Dye-2 Sensitized Solar Cells by Vis−NIR and IR Pump−Probe Spectroscopy, J Phys Chem C
We present femtosecond to nanosecond transient absorption (TA)data on electron injection in dye-sensitized solar cells (DSSCs) fabricated with lowvolatility, commercially relevant electrolytes, with and without added lithium.Results are shown over an extended time range (300 fs−6.3 ns) and extendedwavelength range (800−1400 nm) for both N719 and C106 dyes. Kinetics weremeasured on both TiO2 and noninjecting ZrO2. Using the latter, we havedetermined the spectra and absorption coefficient of N719* across the wavelengthrange. We find an isosbestic point in the TA spectra on TiO2 near 900 nm for allcells, existing from <1 ps to >1 ns. We show how measurements near this isosbesticpoint can give a false impression of uniformly femtosecond injection dynamics inDSSCs. Comparison of dynamics measured at 1200 nm with mid-IR transient absorption measured at 5100 nm confirms amajority proportion of slow (>10 ps) electron injection in these commercially relevant cells. We also comment on a recentpublication which appears to directly contradict the results we present.
Bronstein H, Collado-Fregoso E, Hadipour A, et al., 2013, Thieno [3, 2-b] thiophene-diketopyrrolopyrrole Containing Polymers for Inverted Solar Cells Devices with High Short Circuit Currents, Advanced Functional Materials
Dimitrov SD, Bakulin AA, Nielsen CB, et al., 2012, On the Energetic Dependence of Charge Separation in Low-Band-Gap Polymer/Fullerene Blends, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 134, Pages: 18189-18192, ISSN: 0002-7863
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- Citations: 178
Dimitrov SD, Nielsen CB, Shoaee S, et al., 2012, Efficient Charge Photogeneration by the Dissociation of PC70BM Excitons in Polymer/Fullerene Solar Cells, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, Vol: 3, Pages: 140-144, ISSN: 1948-7185
Dimitrov SD, Dooley CJ, Trifonov AA, et al., 2009, Femtosecond Probing of Optical Phonon Dynamics in Quantum-Confined CdTe Nanocrystals, JOURNAL OF PHYSICAL CHEMISTRY C, Vol: 113, Pages: 4198-4201, ISSN: 1932-7447
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- Citations: 9
Dooley CJ, Dimitrov SD, Fiebig T, 2008, Ultrafast electron transfer dynamics in CdSe/CdTe donor-acceptor nanorods, JOURNAL OF PHYSICAL CHEMISTRY C, Vol: 112, Pages: 12074-12076, ISSN: 1932-7447
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- Citations: 76
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