Photo-stability study of a solution-processed small molecule solar cell system: correlation between molecular conformation and degradation. Issue 1 (31st December 2018)

• Record Type: Journal Article
• Authors: Newman, Michael J.; Speller, Emily M.; Barbé, Jérémy; Luke, Joel; Li, Meng; Li, Zhe; Wang, Zhao-Kui; Jain, Sagar M.; Kim, Ji-Seon; Lee, Harrison Ka Hin; Tsoi, Wing Chung
• Is Part Of: Science and technology of advanced materials. Volume 19:Issue 1(2018)
• Page Start: 194
• Page End: 202
• Publication Date: 2018-12-31
• Subjects: Small molecule solar cells -- BTR -- photobleaching -- burn-in -- Raman spectroscopy -- molecular conformation; 50 Energy Materials -- 101 Self-assembly / Self-organized materials -- 209 Solar cell / Photovoltaics -- 302 Crystallization / Heat treatment / Crystal growth -- 505 Optical / Molecular spectroscopy; Materials -- Technological innovations -- Periodicals; 620.112
• DOI: 10.1080/14686996.2018.1433948
• Languages: English
• ISSNs: 1468-6996

Abstract

Abstract: Solution-processed organic small molecule solar cells (SMSCs) have achieved efficiency over 11%. However, very few studies have focused on their stability under illumination and the origin of the degradation during the so-called burn-in period. Here, we studied the burn-in period of a solution-processed SMSC using benzodithiophene terthiophene rhodamine:[6, 6]-phenyl C71 butyric acid methyl ester (BTR:PC71 BM) with increasing solvent vapour annealing time applied to the active layer, controlling the crystallisation of the BTR phase. We find that the burn-in behaviour is strongly correlated to the crystallinity of BTR. To look at the possible degradation mechanisms, we studied the fresh and photo-aged blend films with grazing incidence X-ray diffraction, UV–vis absorbance, Raman spectroscopy and photoluminescence (PL) spectroscopy. Although the crystallinity of BTR affects the performance drop during the burn-in period, the degradation is found not to originate from the crystallinity changes of the BTR phase, but correlates with changes in molecular conformation – rotation of the thiophene side chains, as resolved by Raman spectroscopy which could be correlated to slight photobleaching and changes in PL spectra. Abstract :