Lattice-Tailored Low-Temperature Processed Electron Transporting Materials Boost the Open-Circuit Voltage of Planar CsPbBr3 Perovskite Solar Cells up to 1.654 V
The electron-transporting layer (ETL) plays a non-negligible role in determining the charge extraction and transfer behaviors from perovskite film under solar irradiation for high efficient perovskite solar cells. Suitable band structure, good conductivity, high electron mobility and low trap state density are preferred for desired ETL to maximize the electricity generation and minimize the charge recombination. Herein, we have demonstrated that the incorporation of antimony (Sb) dopant into the lattice of low-temperature processed TiO2 nanocrystals can effectively suppress the formation of under-coordinated Ti3+ and oxygen vacancies, leading to the improved electronic conductivity and mobility. When assembling into all-inorganic, carbon-based CsPbBr3 planar perovskite solar cells free of noble metal electrode, an enhanced efficiency of 8.91% with an ultra-high open-circuit voltage of 1.654 V and reduced hysteresis from 32% to 15% are achieved based on Sb-doped TiO2 ETL. The mechanism behind this phenomenon is mainly attributed to the improved perovskite film quality and significantly reduced charge recombination. Taking the advantages of low-temperature, low defect state density, high electrical conductivity and mobility into considerations, the Sb-doped TiO2 demonstrates great potential in advanced perovskite solar cells even in flexible devices.