A simulation based incremental study of stable perovskite-on-perovskite tandem solar device utilizing non-toxic tin and germanium perovskite

Abstract

In this investigation, solar cell capacitance simulator (SCAPS) was utilized to numerically analyse an all-tandem solar cell device with non-toxic Methyl-ammonium lead iodide, MAGeI3, as the top cell and Methyl-ammonium tin iodide, MASnI3, as the bottom cell. Prior to numerically simulating the tandem structure, single-junction MAGeI3 and MASnI3 were optimized through investigations of series resistance, bulk defect density, back contact metal (BCM) and choice of electron transport layer (ETL) and hole transport layer (HTL) materials. TiO2, PCBM, SnO2 and ZnO were investigated as ETL candidates while Cu2O, Spiro-OMETAD, PEDOT: PSS, p3HT, CuSCN, CuI, and CuSbS2 were probed as HTL options. Validation studies for MASnI3 were conducted against experimental J-V characteristic parameters, revealing high congruence; a single junction device power conversion efficiency (PCE) value of 6.67% for MASnI3 was established. Additionally, numerically predicted value for single-junction MAGeI3 boasts a PCE of 18.69%, showing robust similarity with previous numerical investigations. The overall single-junction device optimizations highlighted a PCE improvement from 6.67% to 16.46% for single-junction MASnI3 and 18.17–22.73% for single-junction MAGeI3. Device stability was analysed using studies of diffusion length and carrier lifetime. Numerical simulation results demonstrate that the 2-T configuration of MAGeI3-on-MASnI3 output an overall PCE of 19.11%, while the 4-T configuration boasts a high value of 31.01%. Further analysis of device susceptibility at high temperature has been conducted and it indicates temperature increase from 300 K to 375 K decreases PCE from 31.01% to 27.84% (for 4-T) and 18.56–16.14% (for 2-T). In all, the current investigation highlights remarkable potential for the all-perovskite tandem MAGeI3-on-MASnI3 solar device as an economic and non-toxic alternative to traditional Si-based solar devices.