Tuning the crystallization process of perovskite active layer using a functionalized graphene oxide for enhanced photovoltaic performance

The nonoptimized morphology of the active layer has been a major bottleneck for enhancing the performance of perovskite photovoltaic (PV) devices. To address this challenge, the influence of graphene oxide (GO) additive on the device performance was studied using a two-step sequential deposition technique. Depending on the chlorine-functionalized GO (Cl–GO) amount, we observe dramatic changes in the morphology (e.g., grains, grain boundaries, and crystallite size) of the perovskite layer. Resultantly, we find that the optimized amount of Cl–GO is 5.0 volume % in the perovskite precursor PbI₂ solution, which affords the solar-to-electrical power conversion efficiency (PCE) of 15.14% in PV devices with configuration of fluorine-doped tin oxide (FTO)/NiO_x/CH₃NH₃PbI₃ + Cl–O/[6,6]-phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM)/bathocuproine (BCP)/Ag. Importantly, this PCE is about 18% enhancement compared to the PCE of 12.81% in the absence of Cl–GO. Hence, our work provides an insight for fabricating high-efficient perovskite solar cells based on the relationship between additive processing and morphology, affecting device performance.