Ultrawide Band Gap Oxide Semiconductor-Triggered Performance Improvement of Perovskite Solar Cells via the Novel Ga₂O₃/SnO₂ Composite Electron-Transporting Bilayer

The performance of perovskite solar cells (PSCs), especially for the parameters of open-circuit voltage (Voc) and fill factor, is seriously restricted by the unavoidable interfacial charge recombination. In this study, an ultrawide band gap semiconductor material of Ga2O3 is introduced between fluorine-doped tin oxide and SnO2 to regulate the interfacial charge dynamics by forming the Ga2O3/SnO2 electron-transporting bilayer. Ga2O3 has an appropriate conduction band minimum which benefits the electron transport, and at the same time, it has a very deep valence band maximum which could be regarded as an effective blocking layer. Such an innovative structure triggers the advantages of a lower work function and a smoother surface of the electron-transporting bilayer which leads to a high-quality perovskite film. Furthermore, superior hole-blocking properties of the introduced Ga2O3 layer could effectively reduce the interfacial recombination. All the properties could help to improve the extracting and transporting ability of charge carriers synergistically. Finally, the efficiency and stability of PSCs are greatly enhanced. All results suggest that the performance of PSCs could be improved effectively by introducing the ultrawide band gap oxide semiconductor of Ga2O3.