An Exploration of All‐Inorganic Perovskite/Gallium Arsenide Tandem Solar Cells

All‐inorganic perovskite/gallium arsenide (GaAs) tandem solar cells are of great interest for potential space applications. Herein, planar all‐inorganic four‐terminal (4‐T) and two‐terminal (2‐T) perovskite/GaAs tandem solar cells are simulated and optimized, respectively. To achieve higher absorption in the 4‐T configuration, the reflection and parasitic absorption have to be reduced through optimizing the thickness of the perovskite and GaAs base, reducing the thickness of SnO 2 and the organic hole transport layer (HTL), and introducing an antireflection coating, respectively. To balance the short‐circuit current and open‐circuit voltage of the GaAs bottom cell, the doping concentration on GaAs is optimized to 10 18 cm −3 that has resulted in a high power conversion efficiency (PCE) of 30.97%. Based on the results of 4‐T configuration, all‐inorganic perovskites with different halide compositions are used for current matching to achieve a high‐efficiency 2‐T configuration. After studying the effects of defect density and optimizing the doping concentration of the GaAs base, an extremely high PCE of 30.67% is achieved based on 2‐T CsPbIBr 2 /GaAs tandem solar cells. Furthermore, the current mismatching under the AM0 spectrum is eliminated for potential high altitude/space application, and the device offers a very competitive PCE of 27.23% compared with that of traditional GaAs double‐junction tandem solar cells.