Optimizing non-toxic (CH₃NH₃)₃Bi₂I₉ perovskite solar cells by SCAPS-1D

Abstract Low-dimensional bismuth-based perovskite solar cells (PSCs) have demonstrated some benefits over lead-based PSCs for nontoxicity and remarkable stability. These two factors are now the primary concerns in the photovoltaic community. The power conversion efficiency (PCE) of PSCs using the lead Pb-free chemical methylammonium bismuth iodide (CH 3 NH 3 ) 3 Bi 2 I 9 is severely limited due to the poor quality of the photoactive material. The objective of this study was to investigate the intrinsic impacts of (CH 3 NH 3 ) 3 Bi 2 I 9 perovskite by using SCAPS-1D (Solar Cell Capacitance Simulator) to simulate the PSCs and the adjustment of relevant physical parameters to closely match experimental results. Moreover, the cells were optimized based on (CH 3 NH 3 ) 3 Bi 2 I 9 film thickness, total defect density of (CH 3 NH 3 ) 3 Bi 2 I 9 , optical bandgap, and interfacial defects. By conducting a comprehensive analysis of the current–voltage ( J-V ) plots and quantum efficiency ( QE ) feature, the best values of perovskite thickness, bandgap, and defect density were determined to be 100 nm, 1.6 eV, and 10 14 cm −3 , respectively. Furthermore, defects in the interfaces between the electron transport layer (ETL)/(CH 3 NH 3 ) 3 Bi 2 I 9 and hole transport layer (HTL)/(CH 3 NH 3 ) 3 Bi 2 I 9 were added, and their influence on performance was also investigated. Accordingly, the optimum cell has realized a record PCE of 9.043% and a high quantum efficiency exceeding 60%, which is comparable to those of some Pb-free perovskite analogues. The operational temperature calculations showed that all parameters remain relatively constant with increasing temperature. Therefore, the results imply that the simulated Pb-free PSCs can be stable in a thermal environment. The proposed structural layout and optimization approach can encourage more study and actual applications for Pb-free organometallic perovskite solar cells.