Vertically Oriented 1D Capping Layer Enabled by Bilayer Interface Engineering for Efficient and Stable Inverted Perovskite Solar Cells

One-dimensional/three-dimensional (1D/3D) heterostructure perovskite solar cells (PSCs) have attracted considerable attention owing to their exceptional stability. However, conventional 1D perovskites typically align parallel to the substrate or random orientations, which hinders longitudinal carrier transport and consequently leads to generally low device efficiency. Here, we introduce an innovative bilayer interface engineering strategy to induce the formation of vertically oriented 1D perovskite phase along (001) on the surface of 3D perovskite substrate. Compared with 3D sample, the highly ordered 1D/3D perovskite structure enables extended carrier lifetime with rapid interlayer charge transport. More importantly, the vertically oriented 1D capping layer not only tunes energy level alignment but also significantly reduces trap density at the interface, thereby minimizing photovoltage deficit by approximately 350 mV. With these merits, the champion device achieves a maximum power conversion efficiency (PCE) of 25.9%, representing one of the state-of-the-art levels among 1D/3D PSCs reported to date. Under rigorous testing conditions of high-temperature 85 °C and continuous illumination conditions, the 1D/3D devices maintain 83% and 86% of their initial efficiency after 500 and 1200 hours, respectively, demonstrating their excellent practical durability.