Design and optimization of 26.3% efficient perovskite/FeSi₂ monolithic tandem solar cell

A multijunction or tandem technique comprising a wide bandgap top cell and a narrow bandgap bottom cell may be a major stepping stone in an attempt to obtain high-efficiency solar cells. However, easier said than done, it takes a lot to correctly optimize the structure of all the involved layers so as to possibly obtain the desired results. In this paper, a perovskite (CH₃NH₃PbI₃)/FeSi₂ (p-i-n structure) 2-terminal (2-T) monolithic tandem solar cell is proposed and investigated using AFORS-HET v2.5 1D simulator. A hydrogenated amorphous silicon (a-Si:H)/hydrogenated microcrystalline silicon oxide (µc-Si_1−xO_x:H) tunnel recombination junction is employed to interconnect both perovskite and FeSi₂ solar cell for current matching. The influence of both top and bottom absorber layer thickness is analyzed to optimize the device performance. The study reveals an optimized 26.3% efficient perovskite/FeSi₂ monolithic tandem solar cell with J_SC (21.4 mA cm⁻²), V_OC (1.63 V), and FF (74.86%). The results in this paper suggest FeSi₂ material with 0.87 eV bandgap as an alternative for narrow bandgap bottom cell for the perovskite-based tandem solar cells so as to obtain much higher efficiencies.