Tin-based perovskite solar cells with a homogeneous buried interface

Tin-based perovskite solar cells (TPSCs) have emerged as a promising non-toxic and environmentally friendly alternative to lead-based devices^1-3, with certified power conversion efficiencies (PCEs) of inverted architectures now exceeding 16% (refs. ^4-8). Despite an ideal bandgap supporting a theoretical PCE of more than 33%, TPSCs still lag in performance and stability, partly because of suboptimal hole transport layers and a poor buried interface that hinder hole extraction. Here we report (E)-(2-(4',5'-bis(4-(bis(4-methoxyphenyl)amino)phenyl)-[2,2'-bithiophen]-5-yl)-1-cyanovinyl)phosphonic acid at the buried interface, using a molecular film to optimize hole transport layers in inverted TPSCs. This molecular film forms a homogeneous interfacial layer with well-matched energy-level alignment, markedly enhancing hole extraction. Moreover, this approach creates a superwetting underlayer that guides the growth of uniform, high-quality Sn-based perovskite films with reduced defect density and minimized non-radiative recombination losses. The resulting inverted small-area TPSCs demonstrate a record PCE of 17.89% (certified 17.71% under reverse scanning mode). Furthermore, the encapsulated device maintains more than 95% of the initial PCE after 1,344 h of ambient shelf storage and more than 94% after 1,550 h of continuous operation under 1-sun illumination. Notably, we achieve a record PCE of 14.40% for 1 cm² TPSCs, highlighting the scalability of our strategy.