Complete modelling and simulation of all perovskite tandem solar cells

This study reports for the first time a detailed device modelling and simulation of an all-perovskite tandem solar cell consisting of methyl ammonium germanium iodide (MAGeI3) and dipotassium hexabromoplatinate (K2PtBr6) as the light absorber materials for the two sub cells by employing SCAPS 1D simulation tool. The input parameters of perovskite materials including the bandgap, band structure, density of states (DOS) and other relevant optical parameters are estimated by density functional theory (DFT) employing WIEN2k software. The estimated bandgaps of MAGeI3 and K2PtBr6 are found to be 1.82 eV and 1.1 eV respectively, when PBEsol exchange correlation functional of GGA is employed for calculations. The device when modelled in the 2-terminal (2 T) monolithic configuration provides a power conversion efficiency (PCE) of 24.30 %, by inserting a recombination layer made of indium doped tin oxide (ITO) to establish the current matching condition between the top and bottom cells. On the other hand, the device when modelled in the 4 terminal (4 T) stacked layer configuration provides a PCE of 31.68 % when the filtered spectrum is employed as the input solar spectrum for bottom sub cell with K2PtBr6 as absorber material. Further optimization of the input parameters of perovskite, ETL and HTL enhances the PCE of 4-T tandem architecture to 33.10 %.