Non‐Fullerene Acceptor Photo‐Charge Enabled Stretchable Photovoltaic Robustness Under 90% Tensile Strain and 30% Strain Cycles

Abstract

ABSTRACT Stretchable organic solar cells (s‐OSCs) are promising for wearable electronics but suffer from performance degradation under deformation. We improve this situation by leveraging the property of bulk photo‐charge generation in non‐fullerene acceptors (NFAs). Due to its weak dependence on blend morphology, the bulk photo‐charge generation pathway helps alleviate the exciton utilization loss in elastomer‐diluted photoactive layer. Screened by the molecular descriptor of π‐π quadrupole moment (Q ZZ ) and identified by the subsequent photovoltaic performance measurements on single‐component device, AQx‐2F is selected from 130 NFAs with superior bulk photo‐charge generation capability. Incorporating SEEPS via sequential deposition (SD) confers a high fracture strain (ε f ) of 185% in the photoactive layer. Taking advantage of it, the s‐OSC exhibits a power conversion efficiency (PCE) of 9.8% with record photovoltaic robustness. It retains over 80% of its initial PCE both under a high tensile strain of 90% and after 1000 stretching‐releasing cycles at 30% strain. This photoactive layer also enables a flexible semi‐transparent OSC (FST‐OSC) that achieves the light utilization efficiency (LUE) comparable to rigid devices while maintaining mechanical stability. Rooted in emerging photo‐physics of organic photovoltaic materials, this work establishes a new strategy for photovoltaic robust s‐OSCs.