Effects of polymer crystallinity on non-fullerene acceptor based organic solar cell photostability. Issue 45 (21st October 2020)

• Record Type: Journal Article
• Authors: Yi, Xueping; Ho, Carr Hoi Yi; Gautam, Bhoj; Lei, Lei; Chowdhury, Ashraful Haider; Bahrami, Behzad; Qiao, Qiquan; So, Franky
• Is Part Of: Journal of materials chemistry. Volume 8:Issue 45(2020)
• Page Start: 16092
• Page End: 16099
• Publication Date: 2020-10-21
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/d0tc03969a
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : Organic solar cell shows significantly different degradation rate with different donor polymer crystallinity, even the donors and acceptors are all photostable. Abstract : While there has been rapid progress made in the performance of organic photovoltaic (OPV) cells in recent years, the device stability remains a major bottleneck for commercialization. In this work, we blended a stable acceptor (O-IDTBR) with two photostable donors (PTB7-Th and PffBT4T-2OD) having different polymer crystallinity, and the resulting devices show a significant difference in the OPV degradation rate. The OPV devices employing a highly crystalline polymer PffBT4T-2OD as an active layer show a good resistance against light soaking, maintaining 80% of the initial power conversion efficiency (PCE) up to 100 hours, while the devices employing an amorphous polymer PTB7-Th as an active layer show a significant PCE loss in the initial 20 hours mainly due to a rapid loss of the fill factor. By carrying out a comprehensive analysis of the device degradation mechanisms, we conclude that the origin for the PTB7-Th:O-IDTBR device degradation is the formation of mid-gap states under continuous sunlight illumination, leading to a significant drop in electron mobility. Device simulation revealed that deep traps act as charge recombination centers and increase the trap-assisted recombination rate, lowering the FF and J sc .