Interface design based on strain isolation theory with an optimized neutral mechanical plane enables highly ductile and flexible organic photovoltaics

Flexible organic solar cells (FOSCs) have gained significant attention as a promising power source for wearable electronics. PEDOT:PSS is a commonly used functional layer material in FOSCs due to its excellent light transparency and electrical conductivity, especially suitable for interface and electrode materials. However, PEDOT:PSS has poor phase separation, resulting in a rough surface that is unfavorable for contact between upper and lower layers, as well as poor mechanical properties. Herein, we optimize the neutral mechanical plane based on strain isolation and investigate the mechanism of using the poly(TA-DIB-Fe) intermediate protective layer to improve the mechanical properties of PEDOT:PSS layers and FOSCs. The interface design is applied to transparent electrodes on a 25 cm 2 substrate to prepare ultra-flexible modules with a power conversion efficiency (PCE) of more than 14%. The mechanical stability evaluation of the crumpled, thin, and lightweight large-area module is conducted for the first time. The PCE loss is less than 5% after 1000 cycles of bending, and the module maintains good operational performance after crumpling tests. This study presents a novel theory and method for enhancing the tenacity of flexible electronics and provides scientific guidance for the large-scale application of wearable electronics.