Effect of lanthanum doped SnO2 on the performance of mixed-cation mixed-halide perovskite layer

Abstract

Perovskite solar cells (PSCs) have attracted significant attention due to their higher efficiencies and lower fabrication costs. But for the better performance of PSCs, a high-quality electron transport layer (ETL) is crucial. Various ETLs have been employed and among them Tin (IV) oxide (SnO2) has emerged as a promising candidate for electron selective layer in PSCs due to its superior optical and electrical characteristics. However, there is still improvement needed in terms of poor surface morphology and conductivities of SnO2. When SnO2 is used in conjunction with absorber layer in ambient conditions, stability, and charge carrier recombinations at SnO2/perovskite interface remains a serious challenge as well. This study presents the doping of lanthanum (La III), a rare earth element, into SnO2 ETLs to improve the quality and performance of the perovskite layer deposited on top of ETL in ambient condition. With the optimized 4% La (III) doping, SnO2 ETLs become more crystalline with lower parasitic light absorption and surface morphology improves significantly. The improvement in morphology due to doping facilitates larger crystal growth of perovskite in ambient environment. Moreover, Photoluminescence reveals that with optimized level of doping, interfacial charge recombinations are significantly mitigated ensuring smooth injection of electrons into ETL because of superior perovskite film quality. The mixed-cation mixed-halide perovskite film deposited on 4% La:SnO2 ETL show better resistance towards moisture ingress and will substantially contribute to develop long-life of planar PSCs.