Influence of Fullerene Acceptor on the Performance, Microstructure, and Photophysics of Low Bandgap Polymer Solar Cells. Issue 11 (17th January 2017)

• Record Type: Journal Article
• Authors: Huang, Wenchao; Gann, Eliot; Chandrasekaran, Naresh; Prasad, Shyamal K. K.; Chang, Sheng‐Yung; Thomsen, Lars; Kabra, Dinesh; Hodgkiss, Justin M.; Cheng, Yi‐Bing; Yang, Yang; McNeill, Christopher R.
• Is Part Of: Advanced energy materials. Volume 7:Issue 11(2017)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2017-01-17
• Subjects: fullerene derivatives -- morphology -- photophysics -- polymer solar cells -- tandem solar cells; Energy harvesting -- Materials -- Periodicals; Energy conversion -- Materials -- Periodicals; Energy storage -- Materials -- Periodicals; Photovoltaics -- Periodicals; Fuel cells -- Periodicals; Thermoelectric materials -- Periodicals; 621.31
• DOI: 10.1002/aenm.201602197
• Languages: English
• ISSNs: 1614-6832

Abstract

Abstract : 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‐C61 ‐butyric acid methyl ester (PC61 BM), phenyl‐C71 ‐butyric acid methyl ester (PC71 BM), or indene‐C60 bisadduct (ICBA) are correlated. Compared to PC71 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:PC71 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. Abstract : The mixing behavior of a high‐efficiency polymer with various fullerene derivatives is investigated. Compared to solar cells using either PC61 BM or PC71 BM as acceptor, cells using ICBA have a lower efficiency due to a more intermixed morphology. ICBA blends, however, show a higher thermal stability which is exploited in the fabrication of homo‐tandem cells with 9.0% power conversion efficiency.