Eliminating Schottky Barrier via interface state manipulation on phase-tailored 2D/3D perovskite solar cells

Surface passivation via two-dimensional (2D) perovskite has emerged as a promising strategy to enhance the performance of perovskite solar cells (PSCs) due to the effective compensation of interfacial states. However, the in situ grown 2D perovskite passivation layers typically comprise a mixture of multiple dimensionalities at the interface, where band alignment has only been portrayed qualitatively and empirically. Herein, the interface states for precisely phase-tailored 2D perovskite passivated PSCs are quantitatively investigated. In comparison to traditional passivation molecules, 2D perovskite layers based on 4-trifluoromethyl-phenylethylammonium iodide (CF₃PEAI) exhibit an increased work function, introducing desirable downward band bending to eliminate the Schottky Barrier. Furthermore, precisely phase-tailored 2D layers could modulate the interface trap density and energetics. The n = 1 film delivers optimal performance with a hole extraction efficiency of 95.1 %. The optimized n-i-p PSCs in the two-step method significantly improve PCE to 25.40 %, along with enhanced photostability and negligible hysteresis. It highlights that tailoring in the composition and phase distribution of the 2D perovskite layer could modulate the interface states at the 2D/3D interface.