Efficient as-cast thick film small-molecule organic solar cell with less fluorination on the donor

• Published in: Materials chemistry frontiers Vol. 4; no. 1; pp. 26 - 212
• Main Authors: Wang, Kai, Song, Xin, Guo, Xiao, Wang, Yunhao, Lai, Xue, Meng, Fei, Du, Mengzhen, Fan, Dongyu, Zhang, Ren, Li, Gongqiang, Kyaw, Aung Ko Ko, Wang, Jianpu, Huang, Wei, Baran, Derya
• Format: Journal Article
• Language: English
• Published: London Royal Society of Chemistry 01.01.2020
• Subjects: Additives; Charge transport; Chemical synthesis; Donor materials; Energy conversion efficiency; Fluorination; Fluorine; Morphology; Organic chemistry; Photovoltaic cells; Solar cells; Thickness
• ISSN: 2052-1537; 2052-1537
• DOI: 10.1039/c9qm00605b

Herein, two donor materials based on fluorine substituted isatin units ( DI3T-1F , DI3T-2F ) were designed and synthesized for thick-film small molecule solar cells. The devices based on DI3T-1F demonstrate balanced charge transport and less trap-assisted recombination, leading to higher power conversion efficiency (PCE) of 8.33% with a thickness ca. 150 nm compared to DI3F-2F (PCE of 7.32% with thick film at ca. 160 nm) without additives, solvent or thermal annealing treatments. More interestingly, the device based on DI3T-1F small molecules demonstrates good tolerance to active layer thickness from 150 to 300 nm with device performance over 5%. Our results indicate that less fluorine atoms on the donor units can optimize the charge transport, and phase-segregated morphology in small molecule solar cells without the need for post-treatment. Less fluorination, better performance! Devices based on DI3T-1F :PC 71 BM and DI3T-2F :PC 71 BM are fabricated for thick-film small molecule-solar cells (SMSCs). Indeed, the devices based on DI3T-1F the devices based on DI3T-1F show a better tolerance to thickness, giving PCE of 8.33% with ∼150 nm, and 5.43% with ∼300 nm, which are 14% and 50% higher than those of DI3T-2F , respectively.