Multifunctional Polymer Matrix at the Buried Interface Boosting Stability and Efficiency in Perovskite Solar Cells

To drive further advancements, increasing attention has been directed toward optimizing the buried interface in perovskite solar cells, which not only influences carrier accumulation and recombination but also plays a decisive role in the overall quality of deposited perovskite thin films. In this work, sodium hyaluronate is employed to disperse the SnO nanoparticles and facilitate the formation of uniform and compact SnO films. The polymer matrix endows a homogeneously dispersed SnO precursor with long-term stability via steric effect and electrostatic repulsion. This modification effectively eliminates the oxygen vacancies and dangling hydroxyl bonds at the interface. The buried interface is modulated and, in turn, oriented perovskite grains, relaxed residual strain, and well-matched energy alignment enable superior enhancements for obtained devices. Thus, the target device exhibits a champion power conversion efficiency of 25.11% with negligible hysteresis, compared to the control (24.45%). The unencapsulated device still maintains 90% of its original efficiency after being stored at ambient air (humidity >50%) for 1000 h. Hence, this strategy provides a promising approach for enhancing the intrinsic stability of both SnO and perovskite layers, marking a step forward toward the commercialization. [Abstract copyright: © 2025 The Author(s). Small published by Wiley‐VCH GmbH.]