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 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, MoO_x, and PEDOT:PSS;, for their usability as Hole Transfer Mediums (HTMs) as well. The finally optimized configuration FTO/TiO₂/(CsSnI₃/CsSnGeI₃/Cs₃Bi₂I₉)/MoO_x/Au, where 0.8/0.1/0.1 μm of CsSnI₃/CsSnGeI₃/Cs₃Bi₂I₉ is placed as a tri-layer, containing TiO₂ 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/cm², V_OC = 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.