Graphene oxide as dual functional interface modifier for improving wettability and retarding recombination in hybrid perovskite solar cells

The interface between perovskite and the hole transport layer (HTL) is sensitive to photoelectric conversion properties. However, this study shows that the interface wettability of the HTL solution on a perovskite surface could be improved. To address this problem, graphene oxide (GO) with amphiphilic function was used to form a buffer layer between the perovskite and the HTL. After the GO modification, the contact angles of the HTL solution on the perovskite film decreased to zero degrees. X-ray photoelectron spectroscopy revealed that the GO interacts with the perovskite by forming Pb-O bonds, and Raman spectroscopy analysis revealed that the two-dimensional carbon-carbon bonds absorbed the hole transport material, 2,29,7,79-tetrakis-(N,N-di-p-methoxyphenyl-amine)-9,99-spirobifluorene (Spiro-MeOTAD) via pi-pi interactions. The GO layer improved the contact between the perovskite and HTL, resulting in an enhancement of the short circuit current (J(SC)). Moreover, using GO as an insulating buffer layer can retard charge recombination in solar cells, as revealed by EIS measured in dark conditions, leading to a significant increase in the open-circuit voltage (V-OC) and the fill factor (FF). Consequently, the corresponding average efficiency greatly increased by 45.5%, from 10.0% to 14.5%. Therefore, application of GO as a dual-functional buffer layer on the perovskite layer is a useful strategy for preparing highly efficient hybrid perovskite solar cells.