Enhancing performance of low-temperature processed CsPbI₂Br all-inorganic perovskite solar cells using PEO-modified TiO₂

CsPbX₃-based (X = I, Br, Cl) inorganic perovskite solar cells (PSCs) prepared by low-temperature process have attracted much attention because of their low cost and excellent thermal stability. But the high trap state density and serious charge recombination between low-temperature processed TiO₂ film and inorganic perovskite layer interface seriously restrict the performance of all-inorganic PSCs. Here a thin polyethylene oxide (PEO) layer is employed to modify TiO₂ film to passivate traps and promote carrier collection. The impacts of PEO layer on microstructure and photoelectric characteristics of TiO₂ film and related devices are systematically studied. Characterization results suggest that PEO modification can reduce the surface roughness of TiO₂ film, decrease its average surface potential and passivate trap states. At optimal conditions, the champion efficiency of CsPbI₂Br PSCs with PEO-modified TiO₂ (PEO-PSCs) has been improved to 11.24% from 9.03% of reference PSCs. Moreover, the hysteresis behavior and charge recombination have been suppressed in PEO-PSCs.