In-situ self-assembly of hole transport monolayer during crystallization for efficient single-crystal perovskite solar cells.

Single-crystal perovskite solar cells (SC-PSCs) are emerging as a promising technology owing to their intrinsically low defect densities, long carrier diffusion lengths, and enhanced stability compared to their polycrystalline counterpart. However, their performance has been limited by interface-related losses, particularly at the perovskite/charge transport layer, which hinders effective hole extraction and promotes non-radiative recombination. In this work, we introduce a self-assembled monolayer (SAM) deposition strategy that exploits an asymmetric substrate stack configuration during space-confined inverse temperature crystallization (SC-ITC). This configuration triggers an in-situ migration of SAM molecules from the SAM-coated substrate to the uncoated substrate, resulting in a denser and more homogeneous SAM coating than the conventional spin-coating method can achieve. The improved SAM coverage significantly enhances hole extraction. Consequently, our SC-PSCs achieved power conversion efficiency as high as 24.32%.