Efficient non-fullerene organic solar cells with low-temperature solution-processing ferrous oxides as hole transport layer

Non-fullerene organic solar cells (NF-OSCs) have recently attracted enormous attention due to the rapid advance of high-performance photoabsorbers. On the other hand, interfacial materials also play a crucial role in further increasing the device efficiency, but those materials in particular effective hole transporting ones for NF-OSCs are less developed. In this work, three low-temperature solution-processing ferrous oxide films (including CoOx, NiOx, and FeOx) are used as hole transporting layer (HTL) for NF-OSCs. By adding a surfactant and treating with the ultraviolet ozone (UVO), uniform ferrous oxide films with adjustable energy bands are achieved. The NF-OSCs based on PBDB-T-2Cl:IT-4F active layer and using CoOx, NiOx, and FeOx as the HTL afford power conversion efficiencies of 11.4%, 10.2% and 6.4%, respectively. The higher performance of NF-OSCs with the UVO-treated CoOx as the HTL is attributed to its more suitable energy level alignment and better hole transportation property relative to those of the other two counterparts.

Automated summary

In this study, low-temperature solution-processing ferrous oxide films were used as hole transporting layer (HTL) for NF-OSCs, with UVO treatment to achieve uniform films with adjustable energy bands. Among the NF-OSCs using different ferrous oxide films as HTL, the UVO-treated CoOx exhibited the highest performance, attributed to its more suitable energy level alignment and better hole transportation property.