Organic-inorganic perovskite materials have emerged as promising light absorbers in third-generation photovoltaics. Herein, we report, for the first time, the introduction of nitrogen-doped reduced graphene oxide (N-RGO) to the perovskite material composed of FA0.85MA0.15Pb(I0.85Br0.15)3 (FA: formamidinium and MA: methylammonium). By incorporating N-RGO in the perovskite precursor solution, the formation of large perovskite crystals are induced. The increase in crystal size is due to the interaction of the nitrogen groups on N-RGO with formamidinium cations of the perovskite as probed by NMR. As a result of the improved morphology, we observed an improvement in short circuit current (JSC) and the fill factor (FF). Additionally, it was found that graphene sheets, systematically improved open-circuit voltage (VOC), which is believed to be due to passivation of the perovskite surface at the perovskite/Spiro interface. Consequently, N-RGO here has simultaneously two roles of both tuning perovskite morphological and inhibiting recombination resulting in an improvement in all performance parameters. This results in an increase of power conversion efficiency from 17.3% to 18.7%.

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