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

Abstract 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.