Abstract
Solar energy is the most promising and ultimate renewable energy resource, and silicon photovoltaic technology has gone through exciting growth globally. Organic photovoltaics (OPVs) provide solar energy solutions for application scenarios different from existing PV technologies. The organic PV technology, with the synergetic progress in the past decades, has now reached 20% power conversion efficiency (PCE), which has the potential to empower serious new applications using the unique features of OPV-light weight, colorful, semitransparent, flexibility, etc. The concise review focuses on recent device engineering progress in OPV technologies. The background of OPV devices and materials, especially recent nonfullerene acceptors, will first be presented; then, in the recent device engineering progress, the focus will be on active layer engineering to control the morphology of OPV, leading to recent 19%-20% efficiency. The parallel progress in bulk heterojunction (BHJ) and sequential layer-by-layer approaches will be summarized. The transparent OPV (TOPV) devices are of great interest with unique features and provide the broadest design space among all solar technologies. This work reviews the TOPV progress covering the active layer and transparent optical structure designs. The future research directions in OPV are discussed with perspective.