Polyanionic surfactant modulates the substrate surface energy to achieve crystallization control for efficient perovskite solar cells

Abstract

The crystallization process remains critical for fabricating polycrystalline perovskite thin films, however, challenges in controlling this process often induce substantial defects at the substrate/perovskite interfaces, thereby compromising device efficiency and long-term stability. Herein, we introduce a polyanionic surfactant strategy to modulate the heterogeneous crystallization kinetics by tailoring the surface energy of the underlying substrate. Specifically, the incorporation of poly(sodium 4-styrenesulfonate) (PSS-Na) into SnO₂ elevates the surface energy of the electron transport layer, thereby triggering rapid nucleation while inhibiting crystal growth via interactions with organic cations in the perovskite solution. The controlled crystallization process enables the fabrication of high-quality perovskite films characterized by exceptional crystallinity, superior optical absorbance, and optimal interface contact. Consequently, the devices show a notable efficiency improvement from 20.75% to 22.75%. More encouragingly, unencapsulated devices based on PSS-Na exhibit remarkable stability, retaining over 86% of their initial PCE after nearly 1600 hours under a nitrogen atmosphere at room temperature. This strategy offers a promising approach to regulate perovskite crystallization and fabricate efficient, stable perovskite solar cells.