Improving efficiency, air-processability, and stability of organic solar cells with cyclosiloxane additives

Achieving long-term stability and scalable manufacturing under ambient conditions is crucial for the advancement of organic solar cells (OSCs). Additive engineering has proven effective in optimizing active layer morphology and improving device performance. In this study, we systematically investigated the effects of three cyclosiloxane additives (c-3Si, c-4Si, and c-5Si) for the first time. Due to enhanced crystallinity, optimal phase separation, and improved charge carrier dynamics, the c-5Si-processed device exhibited the champion efficiency, outperforming those of control, c-3Si and c-4Si devices. Specifically, the PM6:Y6-based device with c-5Si treatment achieved an impressive PCE of 18.26%. Furthermore, c-5Si processed PM6:L8-BO and D18:L8-BO active layers showed PCEs of 19.35% and 19.70%, respectively, highlighting their universal potential for high-performance devices. Additive c-5Si improved OSC stability, significantly extending the T80 lifetime from 43 to 205 h under 80 °C heating and one sun illumination in the meantime. Additive c-5Si also enabled the fabrication of high-performance active layers under high-humidity conditions (90% RH), providing an effective solution for air processing of OSCs. This work provides a simple yet effective strategy involving cyclosiloxane additives for manipulating active layer morphology, which advances the development of efficient, stable, and scalable OSCs for commercial applications.