Simulation and optimization of a CsSnI3/CsSnGeI3/Cs3Bi2I9 based triple absorber layer perovskite solar cell using SCAPS-1D

This paper demonstrates a numerical study on a novel triple absorber layer-based perovskite photovoltaic cell incorporating Cs3Bi2I9, which offers a relatively high bandgap (2.03 eV) along with superlative thermal stability. Combining it with CsSnGeI3 & CsSnI3 led to enhanced power conversion efficiency in the studied structures. The preliminary simulation performed for the cell configuration, FTO/TiO2/(CsSnI3/CsSnGeI3/Cs3Bi2I9)/Cu2O/Au, resulted in a PCE of 27.59 %, which needed extensive modification. To optimize the device structure, various parameters were rigorously tested, which included (i) tuning the individual thickness of each of the three absorber layers; (ii) studying the applicability of 4 different materials, i.e., TiO2, CdZnS, ZnO, and SnS2, for Electron Transfer Mediums (ETMs); and (iii) examining 5 compounds such as Spiro-OMeTAD, Cu2O, NiO, MoOx, and PEDOT:PSS;, for their usability as Hole Transfer Mediums (HTMs) as well. The finally optimized configuration FTO/TiO2/(CsSnI3/CsSnGeI3/Cs3Bi2I9)/MoOx/Au, where 0.8/0.1/0.1 mu m of CsSnI3/CsSnGeI3/Cs3Bi2I9 is placed as a tri-layer, containing TiO2 as ETM of 0.1 mu m and MoOx as HTM of 0.35 mu m, which had been evaluated as the most-optimized material, exhibits notable photoelectric performance, i.e., JSC = 35.14 mA/cm2, VOC = 1.16 V, FF = 89.16 %, and PCE = 36.34 %. This cell underscores the remarkable potential of CsSnI3/CsSnGeI3/ Cs3Bi2I9 as a perovskite tri-absorber layer along with its suitability for the various ETMs and HTMs that had been evaluated, directing in the path of manufacturing supremely efficient cells.