Promoting the Efficiency and Stability of Nonfullerene Organic Photovoltaics by Incorporating Open-Cage [60]Fullerenes in the Nonfullerene Nanocrystallites.

The device efficiency of PM6 : Y6 -based nonfullerene organic solar cells is fast advanced recently. To maintain organic solar cells (OSCs) with high power conversion efficiency over 16% in long-term operation, however, remains a challenge. Here, a novel non-volatile additive, an open-cage [60]fullerene ( 8OC 60 Me ), is incorporated into PM6:Y6 -based OSCs for high-performance with high durability. With optimized addition of 1.0 wt % 8OC 60 Me , the PCE value of PM6:Y6/8OC 60 Me OSCs can be promoted to 16.5% from 15.0%. Most strikingly, such a high PCE performance can maintain nearly 100% for over 500 h at room temperature; at an elevated operation temperature of 80 °C, the PCE can be stabilized above 15.0% after 45 h of operation. Grazing incidence small- and wide- angle X-ray scattering studies reveal improved orientation and crystallinity of Y6 in a fractal-like network structure of PM6 in PM6:Y6 / 8OC 60 Me films under in situ annealing, parallel to the enhanced electron mobility. Analysis of charge distributions lines up possible van der Waals interaction between the thienyl/carbonyl moiety of 8OC 60 Me and difluorophenyl-based FIC-end groups of Y6 . This result is of great contrast to those devices with the best-selling PC 61 BM as the additives─ 8OC 60 Me might be of interest to be incorporated into future Y6 -based OSCs for concomitantly improved PCE and excellent stability.