The reduction of defect density in perovskite solar cells (PSCs) is the key to suppress the nonradiative recombination, which is critical to achieve high device efficiency. The buried surfaces of perovskite films are more prone to deterioration and defect formation than the bulk and upper surfaces of perovskite films due to continuous solvent and temperature erosion processes. Here, a buried-interface strategy using Rb-based perovskitoids is proposed. The introduction of rubidium halide results in the formation of a deuterogenic Rb-based perovskitoid "scaffold", which effectively enhances the crystallization of the perovskite film and passivates the defects at the buried surface. With this Rb-based perovskitoid strategy, the power conversion efficiency of device increases from 23.26% to 25.14%, thus providing a simple and effective way to improve the performance of PSCs.