Identifying the optimum thickness of electron transport layers for highly efficient perovskite planar solar cells

Abstract

The fabrication of pinhole-free and compact electron transport layers is crucial for achieving high power conversion efficiency of perovskite solar cells. In this work, we report efficient perovskite solar cells using ultrathin TiO₂ films (5–20 nm) as high-quality electron transport layers deposited by the atomic layer deposition technique. The as-prepared solar cells on FTO substrates show a high efficiency of 13.6%, employing the optimum 10 nm thick TiO₂ layer. Furthermore, the flexible cells on PET substrates exhibit an efficiency of 7.2% with low-temperature-processed TiO₂ layers at 80 °C. The effects of layer thicknesses on the cell performance are investigated to reveal the mechanism of high-performance, which is mainly attributed to high transmittance, low leakage current, and low charge transfer resistance and recombination rate. Our major findings are expected to provide a guide to design ultrathin compact electron transport layers for efficient perovskite solar cells.