Stable and low-photovoltage-loss perovskite solar cells by multifunctional passivation

Metal halide perovskite solar cells have demonstrated a high power conversion efficiency (PCE), and further enhancement of the PCE requires a reduction of the bandgap-voltage offset (W_OC) and the non-radiative recombination photovoltage loss (ΔV_OC,nr). Here, we report an effective approach for reducing the photovoltage loss through the simultaneous passivation of internal bulk defects and dimensionally graded two-dimensional perovskite interface defects. Through this dimensionally graded perovskite formation approach, an open-circuit voltage (V_OC) of 1.24 V was obtained with a champion PCE of 21.54% in a 1.63 eV perovskite system (maximum V_OC = 1.25 V, W_OC = 0.38 V and ΔV_OC,nr = 0.10 V); we further decreased the W_OC to 0.326 V in a 1.53 eV perovskite system with a V_OC of 1.21 V and a PCE of 23.78% (certified 23.09%). This approach is equally effective in achieving a low W_OC (ΔV_OC,nr) in 1.56 eV and 1.73 eV perovskite solar cell systems, and further leads to the substantially improved operational stability of perovskite solar cells.