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Influence of Fullerene Acceptor on the Performance, Microstructure, and Photophysics of Low Bandgap Polymer Solar Cells
Author(s) -
Huang Wenchao,
Gann Eliot,
Chandrasekaran Naresh,
Prasad Shyamal K. K.,
Chang ShengYung,
Thomsen Lars,
Kabra Dinesh,
Hodgkiss Justin M.,
Cheng YiBing,
Yang Yang,
McNeill Christopher R.
Publication year - 2017
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201602197
Subject(s) - materials science , acceptor , crystallinity , polymer solar cell , energy conversion efficiency , fullerene , organic solar cell , band gap , quenching (fluorescence) , chemical engineering , photochemistry , polymer , optoelectronics , organic chemistry , composite material , optics , chemistry , physics , condensed matter physics , engineering , fluorescence
The morphology, photophysics, and device performance of solar cells based on the low bandgap polymer poly[[2,6′‐4,8‐di(5‐ethylhexylthienyl)benzo[1,2‐ b ;3,3‐ b ]dithiophene]3‐fluoro‐2[(2‐ethylhexyl)carbonyl]thieno[3,4‐ b ]thiophenediyl (PBDTTT‐EFT) (also known as PTB7‐Th) blended with different fullerene acceptors: Phenyl‐C 61 ‐butyric acid methyl ester (PC 61 BM), phenyl‐C 71 ‐butyric acid methyl ester (PC 71 BM), or indene‐C 60 bisadduct (ICBA) are correlated. Compared to PC 71 BM‐based cells – which achieve a power conversion efficiency (PCE) of 9.4% – cells using ICBA achieve a higher open‐circuit voltage ( V OC ) of 1.0 V albeit with a lower PCE of 7.1%. To understand the origin of this lower PCE, the morphology and photophysics have been thoroughly characterized. Hard and soft X‐ray scattering measurements reveal that the PBDTTT‐EFT:ICBA blend has a lower crystallinity, lower domain purity, and smaller domain size compared to the PBDTTT‐EFT:PC 71 BM blend. Incomplete photoluminescence quenching is also found in the ICBA blend with transient absorption measurements showing faster recombination dynamics at short timescales. Transient photovoltage measurements highlight further differences in recombination at longer timeframes due to the more intermixed morphology of the ICBA blend. Interestingly, a mild thermal treatment improves the performance of PBDTTT‐EFT:ICBA cells which is exploited in the fabrication of a homo PBDTTT‐EFT:ICBA tandem solar cell with PCE of 9.0% and V OC of 1.93 V.