A Commercial Benchmark: Light-Soaking Free, Fully Scalable, Large-Area Organic Solar Cells for Low-Light Applications

Abstract

Low-light applications provide an exciting market opportunity for organic solar cells (OSCs). However, so far, studies have only considered OSCs of limited commercial viability. Herein, the applicability of a fully-scalable, flexible, inverted non-fullerene acceptor (NFA) containing OSC is demonstrated by showing its superior performance to silicon under low-light, achieving 40 µW cm−2 maximum power output at 1300 lx illumination. The effect of parasitic resistance and dark current on low-light performance are identified. Furthermore, an atmosphere sensitive light-soaking (LS) effect, critical for low-light performance and resulting in undesirable S-shaped current-voltage characteristics, is analyzed. By employing different interlayers and photoactive layers (PALs) the origin of this LS effect is identified as poor electron extraction at the electron transport layer (ETL)/PAL interface when the common ETL ZnO is used. Two strategies are implemented to overcome the LS effect: replacement of ZnO with SnO2 nanoparticles to reduce ETL sub-gap electron trap states or tuning the NFA energy levels to optimize interfacial energetics. Finally, the commercial viability of these LS-free devices is demonstrated by fabricating fully printed large-area modules (21.6 cm2) achieving a maximum power output of 17.2 µW cm−2, providing the most relevant example of the currently obtainable performance in commercial low-light OSCs.