Enhanced performance and the related mechanisms of organic solar cells using Li-doped SnO2 as the electron transport layer

Electron transport layer (ETL), facilitating carrier separation and electron extraction, is a key component in organic solar cells (OSCs). Herein, Li-doped tin dioxide (Li:SnO2) prepared based on a simple room-temperature solution process and the following low-temperature annealing is introduced as the ETL of inverted OSCs with the P3HT:PC61BM bulk heterojunction. It is notable that compared to pristine SnO2, Li:SnO2 significantly boosts device performance benefiting from the comprehensive improvement including short-circuit current, open-circuit voltage and fill factor. As a result, ~62.9% increase in power conversion efficiency, i.e., from 2.21% to 3.60% is achieved for the device with optimized Li doping in SnO2 compared to the control device using pristine SnO2. The related mechanisms responsible for the improved performance are investigated. It is believed that this study may provide a valuable exploration to develop high-performance ETLs for OSCs.