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

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.