Enhancing the performance of organic solar cells by modification of cathode with a self-assembled monolayer of aromatic organophosphonic acid

We use a single-molecule self-assembled layer of an aromatic organophosphonic acid (2PACz) to modify the cathode interface layer in inverted organic solar cells (OSCs). The modified OSCs not only have an obvious improvement in power conversion efficiency (PCE), but also demonstrate greatly enhanced air stability. Ultraviolet photoelectron spectroscopy shows that the work function of cathode interlayer after modification by 2PACz is more suitable for electron extraction. In addition, the surface energy is reduced without affecting the film deposition, which will be beneficial to reduce the interfacial traps. As a result, the PCE of OSCs based on the PBDB-T:IT-M system is increased, and its stability in air is greatly improved (remaining 88% of its initial PCE after 555 h in air). Therefore, we provide a new strategy for constructing high-performance non-fullerene OSCs with enhanced air stability.