Enhanced NiOx hole transport layer via graphene assisted annealing for perovskite solar cell

Nonstoichiometric nickel oxide (NiO_x) hole transport layer (HTL) plays an important role in realizing high efficient and hysteresis-free perovskite solar cells (PSCs). Here, we report a precursor additive approach for forming high-quality solution processed NiO_x interlayer. A small quantity of reduced graphene oxide (rGO) is added to the conventional NiO_x precursor. It is found that the modified precursor lead to an improved hole extraction efficiency and uniformity of the NiO_x thin film. Statistically, compared to non-modified NiO_x precursor, perovskite solar cells based on NiO_x:rGO precursor have higher short-circuit current densities (Jsc) and higher fill factors (FF).