Tin-based perovskite solar cells with a homogeneous buried interface.

Abstract

Tin-based perovskite solar cells (TPSCs) have emerged as a promising non-toxic and environmentally friendly alternative to lead-based devices1-3, with certified power conversion efficiencies (PCEs) of inverted architectures now exceeding 16%4-8. Despite an ideal bandgap supporting a theoretical PCE over 33%, TPSCs still lag in performance and stability, partly due to suboptimal hole transport layers and 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, significantly 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 over 95% of the initial PCE after 1344 h of ambient shelf storage and over 94% after 1550 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.