Photostable Inorganic Perovskite Absorber via Thermal Evaporation for Monolithic Perovskite/Perovskite/Silicon Triple-Junction Solar Cells

Monolithic perovskite/perovskite/silicon triple-junction solar cells have the potential to exceed the efficiency limits of perovskite/silicon dual-junction solar cells. However, the development of perovskite/perovskite/silicon triple-junction technology faces several significant hurdles, including the development and integration of a stable high bandgap perovskite absorber into the monolithic structure. Key issues include light-induced halide segregation in mixed halide high bandgap perovskites and the risk of solvent damage to underlying layers during top-cell deposition. To overcome these challenges, we developed a high bandgap, inorganic perovskite absorber, CsPbI2Br, using thermal evaporation at room temperature, eliminating the need for post-deposition annealing. The resulting perovskite films exhibited a bandgap of 1.88 eV and demonstrated good photostability without any signs of halide segregation under continuous illumination probed over 3 h. Additionally, thermal evaporation offers a scalable approach for large-scale production, further enhancing the potential for widespread adoption of this technology. This advancement enabled the incorporation of CsPbI2Br perovskite films into a monolithic perovskite/perovskite/silicon triple-junction device as the top-cell absorber. Consequently, we developed the first triple-junction device with an all-inorganic perovskite top-cell absorber using the thermal evaporation technique, achieving an efficiency of 21%, with an open-circuit voltage of 2.83 V over an active area of 1 cm2. The device underwent 100 h of fixed voltage measurement near maximum power point under ambient conditions without encapsulation. Remarkably, it not only withstood the measurement but also exhibited an improved efficiency of ~22% afterwards, further demonstrating the stability and reliability of our thermally evaporated CsPbI2Br perovskite absorber-based inorganic solar cell for monolithic triple-junction perovskite/perovskite/silicon applications.