Semitransparent organic solar cells: from molecular design to structure–performance relationships

Organic solar cells (OSCs) have drawn tremendous interest because of their potential for low-cost solution processing and color tunability. OSCs with bulk-heterojunction structures offer an attractive pathway to efficiently utilize solar energy and have the potential to make transparent and flexible devices. The design of new materials and optimized device fabrications with visible-light transparency make this technology attractive for various applications, including greenhouses, windows, building structures, etc. In this review, we highlight the developments of fullerene-free acceptors (FFAs) for semitransparent OSCs (ST-OSCs) and device architectures, including transparent electrodes, giving special emphasis to the power conversion efficiency (PCE) and the average visible transparency (AVT).