Exceptional Long Electron Lifetime in Methylammonium Lead Iodide Perovskite Solar Cell Made from Aqueous Lead Nitrate Precursor

Studies on the photoelectronic properties of perovskite solar cells (PSCs) made from non‐PbI 2 precursors are seldom reported. In this study, a series of transient techniques are applied to investigate the charge recombination and trap distribution in an efficient PSC fabricated using a low‐toxicity Pb(NO 3 ) 2 /water protocol. A device with identical conversion efficiency fabricated using a conventional PbI 2 /dimethylformamide protocol is also studied for comparison. Transient photovoltage and time‐resolved photoluminescence analysis reveal that the Pb(NO 3 ) 2 /water‐based device exhibits a long lifetime in both bimolecular and trap‐assisted recombination. However, differential capacitance and differential charging analysis indicate that there are more charges stored in the Pb(NO 3 ) 2 /water‐based perovskite layer, which stretches the energy tail from band edge to midband and should provoke serious trap‐assisted recombination. The exceptional long electron lifetime in the Pb(NO 3 ) 2 /water‐based device is explained by a benign defect inactivation, which originates from water and NO 3 − residues from the aqueous precursor solution and is involved in the formation of perovskite crystal. Consequently, despite the perovskite film made from Pb(NO 3 ) 2 /water protocol possessing high trap density, its photovoltaic device still exhibits a long electron lifetime and superior photovoltaic properties.