A theoretical investigation of the effect of the hole and electron transport materials on the performance of a lead-free perovskite solar cell based on CH3NH3SnI3

This study entails a theoretical investigation of the effect of the hole transport layer (HTL) and electron transport layer (ETL) materials on a lead-free perovskite solar cell based on methylammonium tin iodide (CH3NH3SnI3). The simulations of the solar cells were conducted with the aid of the one-dimensional solar cell capacitance simulator, SCAPS-1D. The initial primary cell with the following architectural design: glass/FTO/WS2/CH3NH3SnI3/P3HT/Au, was simulated to yield a modest power conversion efficiency (PCE) of 10.47%. In an attempt to improve the PCE of this device, several materials were tested as the HTL, and their effects on the PCE were simulated. Subsequently, various ETL materials were tested with what were found to be the best possible HTL materials. The PCE of the primary device increased from 10.47% to over 16% with the utilization of 2,2′,7,7′-tetrakis [N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (spiro-OMeTAD), copper(I) oxide (Cu2O), copper(I) thiocyanate (CuSCN), copper(I) iodide (CuI), and poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno-[3,2-b]thiophene) (D-PBTTT-14) as HTLs. Tungsten disulfide (WS2) was shown to be the best suitable ETL material. The density of defects of the absorber for the devices with tungsten disulfide as the ETL and Cu2O, D-PBTTT-4, CuSCN, spiro-OMeTAD, and CuI as the HTLs, was best at 1.5 × 1017 cm−3, while for the primary device, the best value of the density of defects was 1.5 × 1014 cm−3. Furthermore, the energy barriers at the interface for primary and optimum devices was examined. Additionally, the effect of the external operating temperature on the performance of the devices was investigated. The simulation results allow one to propose the best HTL and ETL materials for high performance of lead-free perovskite solar cells, based on tin.