Interface engineering of high performance all-inorganic perovskite solar cells via low-temperature processed TiO₂ nanopillar arrays

All-inorganic perovskite solar cells suffer from low performance due to unsatisfactory carrier transport and light harvesting efficiency. Semiconductor nanopillar arrays can reduce light reflection loss and suppress exciton recombination dynamics in optoelectronic devices. In all-inorganic perovskite solar cells, few studies employing TiO₂ nanopillar arrays (TiO₂ NaPAs) have been reported to improve the device performance. Herein, well-arranged TiO₂ NaPAs are chosen to enhance the interfacial contact between perovskite and electron transporting layers for improving the carrier transport. Notably, TiO₂ NaPAs can be directly fabricated on rigid/flexible substrates at roughly room temperature by unique glancing angle deposition, which is more available than high-temperature hydrothermal/solvothermal methods. By embedding TiO₂ NaPAs into chemical processable CsPbI₂Br layers, continuous and intimate films are readily formed, guaranteeing large physical contact for facilitating more effective electron injection and charge separation. The vertically grown TiO₂ NaPAs also provide a straightforward electron transporting path to electrodes. In addition, TiO₂ NaPAs can guide the incident light and enhance the light-harvesting ability of CsPbI₂Br films. As a result, the solar cell with TiO₂ NaPAs displays a power conversion efficiency of 11.35% higher than planar control of 10.04%, and exhibits better long-term thermal stability. This strategy provides an opportunity by constructing direct interfacial regulation towards the performance improvement of inorganic perovskite solar cells.