On October 20, news emerged indicating that metal halide perovskites have shown immense promise as materials for flexible and wearable photovoltaic applications. This is attributed to their exceptional optoelectronic properties, solution-processable nature, and mechanical flexibility. Nevertheless, the widely adopted flexible polymer transparent conductive substrates are plagued by several drawbacks, including rough surfaces, inadequate solution wettability, and sluggish thermal conduction. Such issues result in the easy entrapment of dimethyl sulfoxide (DMSO), a high-boiling-point solvent, at the buried interface between the perovskite layer and the underlying transport layer. This entrapment subsequently leads to interface voids, disordered crystallization, and the buildup of residual stress. Consequently, these factors significantly constrain both the optoelectronic conversion efficiency and the mechanical bending stability of flexible devices. Therefore, there is an urgent need to delve into the microscopic mechanisms underlying DMSO retention and devise a straightforward yet effective strategy for eliminating interface residues.