Low-temperature sprayed SnOx nanocomposite films with enhanced hole blocking for efficient large area perovskite solar cells

Scalable fabrication of charge transport layers with high uniformity and compactness is essential for the commercialization of perovskite solar cells (PSCs). Cost-effective deposition of high-quality electron transport layers (ETLs) is a particularly important step to achieve low-cost, efficient and large-area PSCs. Here, an open-air (relative humidity of 40–50%) and low-temperature (≤100 °C) ultrasonic spray coating of tin oxide (SnO2) nanocomposite films incorporating nanocrystalline SnO2 nanoparticles in an amorphous SnOx matrix is demonstrated to fabricate large-area ETLs for planar PSCs. The optimized SnO2/SnOx nanocomposite exhibits significantly enhanced hole-blocking and high-power conversion efficiencies of 18% and 16% for planar PSCs with an active area of 0.2 cm2 and 1 cm2, respectively. More importantly, the devices show little current–voltage hysteresis as well as good shelf-life stability by maintaining ∼90% of the initial performance without encapsulation after 2500 hours storage under inert conditions. Furthermore, high voltages of >6.0 V have been obtained for solar modules of 2.1 cm2 aperture area comprising six sub-cells in series, suggesting that the low-temperature, open-air and fast spray coating is suitable and transferable to deposit large-area charge transport layers for scalable PSCs or other optoelectronic devices.