Efficient large guanidinium mixed perovskite solar cells with enhanced photovoltage and low energy losses

We present a strategy for suppressing the open-circuit voltage (V_oc) loss of perovskite solar cells by incorporating large guanidinium cations (Gua⁺) into a perovskite lattice, leading to a significantly improved V_oc of 1.19 V and an impressive power conversion efficiency of >21%.