An aqueous solution-processed CuOX film as an anode buffer layer for efficient and stable organic solar cells

Abstract

A facile and green method has been developed for the aqueous solution preparation of CuO_X as an anode buffer layer for organic solar cells (OSCs). The CuO_X buffer layer is prepared simply by spin-coating a copper acetylacetonate precursor based aqueous solution onto an ITO substrate at room temperature in ambient air. Hydrogen peroxide (H₂O₂) is used to modify the precursor aqueous solution and can greatly increase the work function of the CuO_X film to improve the hole collection efficiency and the charge transport efficiency. UV-ozone post-treatment of the CuO_X film leads to the fully oxidized state of copper oxide, which significantly improves the performance of OSCs. Through H₂O₂ modification and UV-ozone post-treatment on the CuO_X anode buffer layer, the highest power conversion efficiency of the OSCs based on PTB7:PC₇₁BM blends reaches 8.68%, which is 10% higher than that of the standard PEDOT:PSS anode buffer layer based OSCs. In addition, the devices with the CuO_X buffer layer show much better air stability than those with PEDOT:PSS. Our results indicate that the aqueous solution processed CuO_X with low cost and green solvents is a promising anode buffer layer material for efficient and stable OSCs.