The outstanding advantages of lightweight and flexibility enable flexible perovskite solar cells (PSCs) to have great application potential in mobile energy devices. Due to the low cost, low-temperature processibility, and high electron mobility, SnO2 nanocrystals have been widely employed as the electron transport layer in flexible PSCs. To prepare high-quality SnO2 layers, a monodispersed nanocrystal solution is normally used. However, the SnO2 nanocrystals can easily aggregate, especially after long periods of storage. Herein, we develop a green and cost-effective strategy for the synthesis of high-quality SnO2 nanocrystals at low temperatures by introducing small molecules of glycerol, obtaining a stable and well-dispersed SnO2-nanocrystal isopropanol dispersion successfully. Due to the enhanced dispersity and super wettability of this alcohol-based SnO2-nanocrystal solution, large-area smooth and dense SnO2 films are easily deposited on the plastic conductive substrate. Furthermore, this contributes to effective charge transfer and suppressed non-radiative recombination at the interface between the SnO2 and perovskite layers. As a result, a greatly enhanced power conversion efficiency (PCE) of 21.8% from 19.2% is achieved for small-area flexible PSCs. A large-area 5 cm × 5 cm flexible perovskite solar mini-module with a champion PCE of 16.5% and good stability is also demonstrated via this glycerol-modified SnO2-nanocrystal isopropanol dispersion approach.
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