Sb2Se3 as a bottom cell material for efficient perovskite/Sb2Se3 tandem solar cells

Antimony selenide (Sb2Se3) semiconducting material possesses a band gap of 1.05–1.2 eV and has been widely applied in single-junction solar cells. Based on its band gap, Sb2Se3 can also be used as the bottom cell absorber material in tandem solar cells. More importantly, Sb2Se3 solar cells exhibit excellent stability with nontoxic compositional elements. The band gap of organic–inorganic hybrid perovskite is tunable over a wide range. In this work, we demonstrate for the first time a perovskite/antimony selenide four-terminal tandem solar cell with a specially designed and fabricated transparent electrode for an optimized spectral response. By adjusting the thickness of the transparent electrode layer of the top cell, the wide-band-gap perovskite top solar cell achieves an efficiency of 17.88%, while the optimized antimony selenide bottom cell delivers a power conversion efficiency of 7.85% by introducing a double electron transport layer. Finally, the four-terminal tandem solar cell achieves an impressive efficiency exceeding 20%. This work provides a new tandem device structure and demonstrates that antimony selenide is a promising absorber material for bottom cell applications in tandem solar cells.