High-throughput screening of wide-bandgap perovskites for efficient perovskite/silicon tandem solar cells

• High-throughput DFT screening of 303 perovskite compositions reveals distinct roles of A-site and X-site alloying. • A-site alloying (MA/FA) brackets but never reaches the optimal ∼1.70 eV bandgap for tandem top cells. • X-site Br incorporation enables precise bandgap tuning to ∼1.70 eV with enhanced optical performance. • FAPb(I 0.5 Br 0.5 ) 3 and MAPb(I 0.75 Br 0.25 ) 3 identified as optimal compositions with superior absorbance and minimized segregation risk. • Provides a robust theoretical framework for rational design of bandgap-engineered perovskite top cells in tandem photovoltaics. Bandgap-tunable metal-halide perovskites are critical for high-efficiency perovskite/silicon tandem solar cells, yet the respective roles of A- and X-site alloying remain contentious. Here, a high-throughput density-functional-theory (DFT) workflow was deployed to screen 303 compositional configurations across four doping series — MA x FA 1-x PbI 3 , MA x FA 1-x PbBr 3 , FAPb(I 1-x Br x ) 3 , and MAPb(I 1-x Br x ) 3 . After ground-state energy filtering, every configuration was evaluated for bandgap, band alignment, tolerance factor,and formation energy. A-site doping in MA x FA 1-x PbI 3 and MA x FA 1-x PbBr 3 bracketing but never reaches the optimum top-cell bandgap target of ∼1.70 eV . In contrast, bandgap can be continuously tuned to 1.70 eV by progressive X-site Br incorporation, which induces a monotonic blue shift in absorption peak. FAPb(I 0.5 Br 0.5 ) 3 realizes this ideal bandgap together with superior absorbance, identifying it as the optimum composition in the FAPb(I 1-x Br x ) 3 series. Likewise, MAPb(I 0.75 Br 0.25 ) 3 attains ∼1.70 eV with only 25 % Br, minimizing halide-segregation risk while preserving the same advantageous optical signatures, and is thus the most promising candidate in the MAPb(I 1-x Br x ) 3 . These quantitative structure–property relations provide a robust theoretical platform for the rational design of bandgap-engineered perovskite top cells in tandem photovoltaics.