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

Abstract This paper demonstrates a numerical study on a novel triple absorber layer-based perovskite photovoltaic cell incorporating Cs 3 Bi 2 I 9 , which offers a relatively high bandgap (2.03 eV) along with superlative thermal stability. Combining it with CsSnGeI 3 & CsSnI 3 led to enhanced power conversion efficiency in the studied structures. The preliminary simulation performed for the cell configuration, FTO/TiO 2 /(CsSnI 3 /CsSnGeI 3 /Cs 3 Bi 2 I 9 )/Cu 2 O/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., TiO 2 , CdZnS, ZnO, and SnS 2 , for Electron Transfer Mediums (ETMs); and (iii) examining 5 compounds such as Spiro-OMeTAD, Cu 2 O, NiO, MoO x , and PEDOT:PSS;, for their usability as Hole Transfer Mediums (HTMs) as well. The finally optimized configuration FTO/TiO 2 /(CsSnI 3 /CsSnGeI 3 /Cs 3 Bi 2 I 9 )/MoO x /Au, where 0.8/0.1/0.1 μm of CsSnI 3 /CsSnGeI 3 /Cs 3 Bi 2 I 9 is placed as a tri-layer, containing TiO 2 as ETM of 0.1 μm and MoO x as HTM of 0.35 μm, which had been evaluated as the most-optimized material, exhibits notable photoelectric performance, i.e., J SC = 35.14 mA/cm 2 , V OC = 1.16 V, FF = 89.16 %, and PCE = 36.34 %. This cell underscores the remarkable potential of CsSnI 3 /CsSnGeI 3 /Cs 3 Bi 2 I 9 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. • An all inorganic triple absorber (CsSnI₃/CsSnGeI₃/Cs₃Bi₂I₉) solar cell was investigated using SCAPS-1D. • Optimized charge carrier extraction was ensured through proper band alignment. • TiO₂ and MoOₓ were employed as electron and hole transport layers due to their superior performance. • An increase in defect density within the absorber layer resulted in a decline in all device parameters. • Maximum PCE = 36.34 % was found for FTO/TiO 2 /(CsSnI 3 /CsSnGeI 3 /Cs₃Bi₂I₉)/MoO x /Au device.