Highly efficient organic solar cells with improved stability enabled by ternary copolymers with antioxidant side chains

Abstract The stability of organic solar cells (OSCs) remains a major concern for their ultimate industrialization due to the photo, oxygen, and water susceptibility photoactive materials. Usually, antioxidant additives are blended as radical scavengers into active layer. However, it will induce intrinsic morphology instability adversely affect efficiency long-term stability. Herein, dibutylhydroxytoluene (BHT) group has been covalently linked onto side chain benzothiadiazole (BT) unit, series ternary copolymers D18-Cl-BTBHTx (x = 0, 0.05, 0.1, 0.2) with varied ratio BHT-containing chains have synthesized. It was found that introduction BHT would negligible effect on photophysical properties electronic levels, D18-Cl-BTBHT0.05: Y6-based OSC achieved highest power conversion (PCE) 17.6%, which is higher than those based layer additives. More importantly, unencapsulated device retained approximately 50% initial PCE over 30 hours operation under ambient conditions, significantly outperforming control D18-Cl (90% degradation in after h). This work provides new structural design strategy OSCs simultaneously improved