A (CH3NH3)3Bi2I9 Perovskite Based on a Two‐Step Deposition Method: Lead‐Free, Highly Stable, and with Enhanced Photovoltaic Performance

Despite achieving a higher efficiency, lead‐based perovskite solar cells (PSCs) suffer from leakage of highly toxic Pb into the atmosphere. On the contrary, methyl ammonium bismuth halide (MBI) has gained enormous attention as a light absorber because of its low toxicity and air stability. Herein, we developed high‐performance, lead‐free PSCs by employing a modified two‐step deposition method with FTO/CL‐TiO2/m‐TiO2/MBI/Spiro‐MEOTAD/Au device architecture [where FTO: fluorine doped tin oxide; MBI: (MA)3Bi2I9; MEOTAD: 2,2′,7,7′‐tetrakis‐(N,N‐di‐4‐methoxyphenylamino)‐9,9′‐spirobifluorene]. The PSCs fabricated by the two‐step deposition method showed a good power‐conversion efficiency of 0.41 %, along with a high open circuit voltage of 870 mV, and were found to be highly stable up to 60 days under atmospheric conditions (humidity ∼40–50 %). The film quality of the MBI was found to be superior by introducing modified two‐step deposition method over one‐step deposition.