Optoelectronic and Photovoltaic Properties of (NH4)3Bi2I9: A Perovskite‐like Energy Material for Pb‐free Perovskite Solar Cells

Abstract Recent few years have witnessed a tremendous surge in the design and fabrication of lead (Pb)‐free perovskite or perovskite‐like materials for the development of perovskite solar cells (PSCs). Bismuth halide perovskite materials such as (CH 3 NH 3 ) 3 Bi 2 I 9 , Cs 3 Bi 2 I 9 and FA 3 Bi 2 I 9 have been utilized as highly efficient perovskite light absorbers in terms of aerobic stability. Herein, we have investigated the optoelectronic properties of the (NH 4 ) 3 Bi 2 I 9 perovskite and employed as light absorber in the construction of Pb free PSCs. Solvent engineering approach was utilized to improve the photovoltaic performance of the (NH 4 ) 3 Bi 2 I 9 perovskite based PSCs. The probable HOMO and LUMO energy level values of the (NH 4 ) 3 Bi 2 I 9 perovskite were also investigated and the band gap of the (NH 4 ) 3 Bi 2 I 9 perovskite was found to be of 2.1 eV. The developed PSCs device exhibited the power conversion efficiency (PCE) of ∼0.6%.