Electro-active polymer acceptor additives for high-efficiency and mechanically durable intrinsically-stretchable polymer solar cells

Abstract

The polymer donor and small molecule acceptor are key components for achieving high power conversion efficiency in organic solar cells. Small molecules have the advantage of forming well-defined crystalline structures within the active layer, leading to improved electrical properties. However, such structures can often compromise the mechanical properties of the active layer. Therefore, it is crucial to explore electrically active polymer electron acceptors that exhibit excellent flexibility and durability, to simultaneously enhance the photovoltaic efficiency and mechanical properties of organic solar cells. In this study, we introduced a novel polymer electron acceptor, P(NDI2OD-TCVT), based on naphthalene diimide (NDI). By incorporating a cyano unit into the polymer backbone, we were able to mitigate the excessive crystalline properties and enhance the amorphous characteristics of the material. This, in turn, facilitated the formation of entangled molecules and interconnected networks within the active layer. As a result, the electrical properties of the organic solar cells were significantly improved, achieving a remarkable power conversion efficiency (PCE) of 16.8%. Moreover, we demonstrated the feasibility of flexible polymer solar cells (IS-PSCs) with enhanced mechanical properties. IS-PSCs incorporating 10 wt% of P(NDI2OD-TCVT) achieved a PCE of 12.55% and retained 80% of the initial photovoltaic efficiency even after undergoing 100 cycles of 20% deformation, showcasing their excellent mechanical durability.