Sb 2Se 3 as a bottom cell material for efficient perovskite/Sb 2Se 3 tandem solar cells

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