Back Cover Image, Volume 8, Number 9, May 2026

Back cover image: PC61BM, a common electron transport material in p-i-n perovskite solar cells, often suffers from aggregation and poor interfacial contact, resulting in low morphological stability. Tin-based perovskites further exacerbate this issue due to their intrinsically rough and defect-rich surfaces, which hinder efficient charge extraction and accelerate degradation. In article number CEY270123, Ryu et al. introduce a conjugated polymer-incorporated PC61BM layer that forms a smooth, uniform, and trap-suppressed interface with tin perovskite films. This modified PC61BM effectively enhances electron transport, minimizes interfacial recombination, and significantly improves device stability. The study offers a scalable route toward durable, lead-free perovskite photovoltaics.