Growth Temperature Influence on Atomic-Layer-Deposited In₂O₃ Thin Films and Their Application in Inorganic Perovskite Solar Cells

Recently, indium oxide (In₂O₃) thin films have emerged as a promising electron transport layer (ETL) for perovskite solar cells; however, solution-processed In₂O₃ ETL suffered from poor morphology, pinholes, and required annealing at high temperatures. This research aims to carry out and prepare pinhole-free, transparent, and highly conductive In₂O₃ thin films via atomic layer deposition (ALD) seizing efficiently as an ETL. In order to explore the growth-temperature-dependent properties of In₂O₃ thin film, it was fabricated by ALD using the triethyl indium (Et₃In) precursor. The detail of the ALD process at 115-250 °C was studied through the film growth rate, crystal structure, morphology, composition, and optical and electrical properties. The film growth rate increased from 0.009 nm/cycle to 0.088 nm/cycle as the growth temperature rose from 115 °C to 250 °C. The film thickness was highly uniform, and the surface roughness was below 1.6 nm. Our results confirmed that film's structural, optical and electrical properties directly depend on film growth temperature. Film grown at ≥200 °C exhibited a polycrystalline cubic structure with almost negligible carbon impurities. Finally, the device ALD-In₂O₃ film deposited at 250 °C exhibited a power conversion efficiency of 10.97% superior to other conditions and general SnO₂ ETL.