Lattice-tailored low-temperature processed electron transporting materials boost the open-circuit voltage of planar CsPbBr3 perovskite solar cells up to 1.654 V

Abstract

The electron-transporting layer (ETL) plays a non-negligible role in determining the charge extraction and transfer behaviors from perovskite films under solar irradiation for high efficiency perovskite solar cells. A suitable band structure, good conductivity, high electron mobility and low trap state density are preferred for the desired ETL to maximize the electricity generation and minimize the charge recombination. Herein, we have demonstrated that the incorporation of antimony (Sb) dopants into the lattice of low-temperature processed TiO₂ nanocrystals can effectively suppress the formation of under-coordinated Ti³⁺ and oxygen vacancies, leading to improved electronic conductivity and mobility. When assembling into all-inorganic, carbon-based CsPbBr₃ planar perovskite solar cells free of noble metal electrodes, an enhanced efficiency of 8.91% with an ultra-high open-circuit voltage of 1.654 V and reduced hysteresis from 32% to 15% is achieved based on the 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 consideration, the Sb-doped TiO₂ ETL demonstrates great potential in advanced perovskite solar cells even in flexible devices.