The edge of halide perovskites: surfaces and interfaces drive solar efficiency and stability

compositional and morphological optimization. Outstanding challenges include refined control over parasitic loss pathways, such as surface recombination at charge harvesting electrodes, and long-term stability. In this review, we identify critical design criteria of interfaces to promote both performance and durability. Key points of consideration include near-surface chemistry-electronic property connections underpinning charge harvesting selectivity, how defect-mediated recombination at interfaces lowers device performance, and how interfacial instabilities underlie many failure mechanisms in perovskite solar cells. This review surveys current materials strategies for interfacial engineering, including transport layer design and surface passivation, as well as advanced characterization techniques that offer insights into materials surfaces and buried interfaces. By integrating theoretical understanding with empirical approaches, we aim to provide a framework for rational interface design to unlock scalable, stable, and efficient perovskite photovoltaics.