Engineering high-performance and air-stable PBTZT-stat-BDTT-8:PC61BM/PC71BM organic solar cells

High-performance air-stable PBTZT-stat-BDTT-8 organic solar cells were fabricated using mixed C60/C70 fullerene acceptors. Normal-architecture devices using PBTZT-stat-BDTT-8 with PC71BM produced a power conversion efficiency (PCE) of 9.38%. An inverted-architecture, which possesses higher stability, was fabricated using a more economical PC61BM and PC71BM mixture with solution-processed PEDOT:PSS on top and produced a PCE of 8.15%. Exploiting the viscous nature of PBTZT-stat-BDTT-8, the slow evaporation effect was utilised to achieve an even higher efficiency of 8.73%. A stability test was conducted under operating conditions and our devices showed remarkably higher stability compared with PTB7-based devices.