Room-Temperature Spray Deposition of Large-Area SnO 2 Electron Transport Layer for High Performance, Stable FAPbI 3 -Based Perovskite Solar Cells.

The performance and scalability of perovskite solar cells (PSCs) is highly dependent on the morphology and charge selectivity of the electron transport layer (ETL). This work demonstrates a high-speed (1800 mm min -1 ), room-temperature (25 °C-30 °C) deposition of large-area (62.5 cm 2 ) tin oxide films using a multi-pass spray deposition technique. The spray-deposited SnO 2 (spray-SnO 2 ) films exhibit a controllable thickness, a unique granulate morphology and high transmittance (≈85% at 550 nm). The performance of the PSC based on spray-SnO 2 ETL and formamidinium lead iodide (FAPbI 3 )-based perovskite is highly consistent and reproducible, achieving a maximum efficiency of ≈20.1% at an active area (A) of 0.096 cm 2 . Characterization results reveal that the efficiency improvement originates from the granular morphology of spray-SnO 2 and high conversion rate of PbI 2 in the perovskite. More importantly, spray-SnO 2 films are highly scalable and able to reduce the efficiency roll-off that comes with the increase in contact-area between SnO 2 and perovskite film. Based on the spray-SnO 2 ETL, large-area PSC (A = 1.0 cm 2 ) achieves an efficiency of ≈18.9%. Furthermore, spray-SnO 2 ETL based PSCs also exhibit higher storage stability compared to the spin-SnO 2 based PSCs.