Methanol solvent treatment: A simple strategy to significantly boost efficiency and stability of air-processed ternary organic solar cells based on PTB7-Th:PCDTBT:PC70BM

Abstract

Abstract The power conversion efficiency (PCE) of ternary organic solar cells (OSCs) based on PTB7-Th:PCDTBT:PC70BM with good air stability needs to be further improved. We report here 2 min methanol solvent treatment of the active layer of ternary OSCs based on PTB7-Th:PCDTBT:PC70BM can significantly boost efficiency up to 9.60%, which exhibits a 30.4% improvement compared to that of 7.36% for the device without methanol solvent treatment. The performance improvement is mainly due to the enhanced light absorption, efficient charge transfer and optimized bulk morphology in the ternary active layer. Meanwhile, the air stability of the methanol solvent treated device can be clearly improved by the removal of residual DIO in the active layer. The PCE of the 2 min methanol treated device could retain 95.4% of the initial value after 7 days of storage in air. Our results indicate that methanol solvent treatment is a simple but effective strategy to boost efficiency and air stability of ternary OSCs based on PTB7-Th:PCDTBT:PC70BM.