Yttrium oxide engineered substrate enables improved durability for perovskite solar cells

Transparent conductive oxides (TCOs)—foundation of perovskite solar cells (PSCs)—have long been assumed to be stable, and thus their impact on device longevity is frequently overlooked. Herein, we unveil that fluorine doped tin oxide (FTO) suffers from instability under operational stress, exacerbating PSC stability issue. To address this issue, we propose a universal interface engineering strategy employing a scalable thermal evaporation followed by natural oxidation to form an atomically bonded yttrium oxide (Y2O3) to strengthen structural stability of FTO. Evaporated yttrium effectively anchors a portion of lattice oxygen within FTO, preventing elemental dissociation. Moreover, the formed Y2O3 featured conformal deposition on rough FTO increases the interfacial adhesion energy, establishing a robust barrier against ion diffusion and carrier nonradiative recombination loss. This approach fortifies the structural integrity of the PSC, leading to dramatically improved operational stability. Unencapsulated devices exhibit negligible performance loss after 1,200 h of continuous illumination. Notably, we achieve power conversion efficiencies of 26.48% (certified at 26.12%) in regular (n–i–p) architectures, 26.34% in inverted (p–i–n) configurations, and 28.47% in tandem structures–among one of the highest reported in their respective categories–underscoring its strong generality and potential for commercialization. The impact of fluorine doped tin oxide (FTO) on device longevity has been overlooked. Here, the authors employ thermal evaporated yttrium oxide to strengthen structural stability of FTO, achieving maximum efficiency of 26.48% and 28.47% in regular and all-perovskite tandem structures, respectively.