Low-TemperaturePlasma-Assisted Atomic-Layer-DepositedSnO2 as an Electron Transport Layer in Planar PerovskiteSolar Cells

摘要

In this work, we present an extensive characterization of plasma-assisted atomic-layer-deposited SnO2 layers, with the aim of identifying key material properties of SnO2 to serve as an efficient electron transport layer in perovskite solar cells (PSCs). Electrically resistive SnO2 films are fabricated at 50 °C, while a SnO2 film with a low electrical resistivity of 1.8 × 10^–3 Ω cm, a carrier density of 9.6 × 10¹⁹ cm^–3, and a high mobility of 36.0 cm²/V s is deposited at 200 °C. Ultraviolet photoelectron spectroscopy indicates a conduction band offset of ∼0.69 eV at the 50 °C SnO2/Cs0.05(MA0.17FA0.83)0.95Pb(I2.7Br0.3) interface. In contrast, a negligible conduction band offset is found between the 200 °C SnO2 and the perovskite. Surprisingly, comparable initial power conversion efficiencies (PCEs) of 17.5 and 17.8% are demonstrated for the champion cells using 15 nm thick SnO2 deposited at 50 and 200 °C, respectively. The latter gains in fill factor but loses in open-circuit voltage.Markedly, PSCs using the 200 °C compact SnO2 retaintheir initial performance at the maximum power point over 16 h undercontinuous one-sun illumination in inert atmosphere. Instead, thecell with the 50 °C SnO2 shows a decrease in PCE ofapproximately 50%.