Modular Perovskite Solar Cells with Cs0.05(FA0.85MA0.15)0.95Pb(I0.85Br0.15)3 Light-Harvesting Layer and Graphene Electrode

Perovskite solar cells (PSCs) are emerging as a promising next-generation photovoltaic device with unprecedented advantages. However, the use of expensive and unstable noble metals as back electrodes seriously limits the large-scale application of PSCs. Modular carbon electrode PSCs (C-PSCs), i.e., the final PSCs were assembled with two individual elements (semi-cell A and charge collector B) under pressure, have been demonstrated as an excellent solution to the serious limitations caused by noble metal electrodes. Modular C-PSCs have been synthesized, where simple spray-coated graphene was used as a carbon electrode and an A-site triple cation mixed composition perovskite Cs0.05(FA0.85MA0.15)0.95Pb(I0.85Br0.15)3 as the light-harvesting layer. For comparison, conventional Au electrode PSCs (A-PSCs) were also fabricated using the same perovskite composition. Despite its slightly inferior power conversion efficiency, 18.88% for C-PSCs compared with 19.37% for A-PSCs, the C-PSCs exhibit significantly improved stability compared to the A-PSCs, which was mainly attributed to the hydrophobic nature of the carbon electrode and enhanced photochemical stability due to the incorporation of Cs+ cations. Moreover, models to analyze the photogeneration and carrier transport properties of C-PSCs and A-PSCs have been proposed based on electrochemical impedance spectroscopy and current density–voltage curve measurements.