Advanced computational modeling and performance optimization of 3D/3D bilayer perovskite heterojunction in monolithic tandem photovoltaic device

All-Perovskite tandem solar cells can generate high efficiency with long-term stability at low cost. Metal halide perovskite photovoltaic devices designed with tandem architectures could potentially enhance the efficiency of commercial single-junction solar cells from ∼20 % to ∼30 %. This work presents the design of an all-perovskite tandem solar cell of high efficiency made of perovskite absorber FA_0.8Cs_0.2Pb(I_0.6Br_0.4)₃ of 1.77 eV energy bandgap in the top cell and FA_0.7MA_0.3Pb_0.5Sn_0.5I₃ of 1.25 eV energy bandgap in the bottom cell. The narrow bandgap perovskite bottom sub-cell is designed with 3D/3D bilayer perovskite heterojunction between the perovskite absorber layer and electron transport layer to decrease interfacial non-radiative recombination. The standalone solar cell designs are optimized by refining parameters such as thickness, shallow donor/acceptor densities, bulk and interfacial trap densities, etc. These optimized designs are consequently integrated to design a tandem solar cell at current matching conditions and a comprehensive analysis of the designs is done. The designed tandem solar cell has a high efficiency of 30.8 % with short-circuit current density (J_SC) of 15.9 mA/cm², open-circuit voltage (V_OC) of 2.25 V, and high fill factor (FF) of 86 %. This simulated design contributes valuable insights for the development of tandem solar cells, supported by comparisons with prior experimental and computational results. The effect of Radiative recombination, Auger Recombination, series resistance and shunt resistance is also analyzed.