Abstract
Perovskite solar cells (PSCs) have attracted wide publicity via their excellent photoelectric properties. Nevertheless, the relative low formation energy and soft lattice of perovskite make it vulnerable to external environmental factors, especially the moisture. Inevitably, water molecules would remain in PSCs modules during practical production. Trace amounts of free water could not only destroy perovskite film, but also trigger metal electrode oxidation forming “snail tracks”. Most previous reports simply block perovskite film contact with water, ignoring the migration damage of free water in PSCs system. Herein, Sorbitan Monolaurate (Span 20), with multiple hydroxyl, ether, carbonyl groups and long alkyl chain, was adopted to post-treat the surface of perovskite. The hydrophilic groups can effectively absorb the slight free water in PSCs system, while the hydrophobic group would protect perovskite film from erosion. Shockingly, the modified perovskite films are hydrophilic, and present outstanding water stability, soaking in water over 360 min. The perovskite films morphology, crystallinity, photoelectric properties and decomposition processes are also improved by Span 20 passivation. In addition, the Span 20/IPA post-treatment has a large concentration operation window (5–100 mg/mL). The optimum power conversion efficiency (PCE) of devices increased to 22.13%, and preserved over 90% of the initial PCE during 29 d air aging (humidity: 60 ∼ 80 RH). This work overturns the popular concept of perovskite water stability, and provides a novel sight to improve the long-term stability of perovskite.
Published Version
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