Reduced graphene oxide in perovskite solar cells: the influence on film formation, photophysics, performance, and stability

Mixed-halide perovskites of the type Cs(x)FA(1-x)Pb(BryI1-y)(3) are promising materials for highly efficient single junction and tandem solar cells. This work details how RGO interacts with the perovskite, influencing film formation and its physico-chemical properties. RGO was introduced into the precursor solution to study how reduced graphene oxide (RGO) interferes with the crystallization, morphology, and optoelectronic properties of the perovskite film. By in situ GIWAXS experiments, a decrease in the rate of formation of the bulk perovskite phase was observed during the spin-coating and annealing processes. SEM-FEG images confirmed an increase in the grain size of the perovskite film that contained RGO. The most outstanding results were related to the stability of the devices. Devices with RGO-20 h (reduced for 20 hours) exhibited a higher stability, confirming that the films formed by larger grains have a slower rate of degradation.