Semi-transparent quaternary organic blends for advanced photovoltaic applications
In spite of enormous promise in a multitude of applications, semi-transparent organic photovoltaics (ST OPVs) relatively lag behind opaque OPVs in the efficiency, and further efforts are imperative to improve their performance while preserving their transparency and tunable color perceptivity. Here, we develop highly efficient ST OPVs based on quaternary blends (Q-blend) involving non-fullerene small molecules, and demonstrate their realistic application in four-terminal (4T) tandem PVs. The ST quaternary OPV (Q-OPV) exhibits superior power conversion efficiencies (PCEs) higher than those of the state-of-the-art ST OPVs under any irradiation conditions, while retaining high transparency and the possibility of implementing various colors. In particular, we achieve the first PCE value exceeding 15% (~15.46%) under indoor lighting among the ST OPVs reported to date. The 4T tandem configurations based on a ST Q-OPV with diverse opaque PVs demonstrate broadband photon harvesting, with aesthetic functions rendered from the color-codable ST Q-OPV. The benefits of the Q-blend platform, including efficient operation under any irradiation circumstance (both indoor and outdoor lighting) and device color codability via tuning the quaternary components, can further expand the applicability of the ST Q-OPV to various practical applications.