In Situ Dynamic Regulation of Strain at the Buried Interface of Stable Perovskite Solar Cells

• • Liquid medium annealing (LMA) reduces residual strain at the buried interface, as evidenced by suppressed d-spacing variation of the (001) facet at 85 °C, leading to improved thermal stability. • • Target films exhibit enhanced mechanical uniformity, with modulus mapping showing a more homogeneous distribution compared to control films, which is critical for preventing stress-induced failure. • • Diurnal cycling tests (12 h MPPT at 85 °C and 12 h dark at room temperature) demonstrate that LMA-treated devices retain a higher fraction of initial performance, indicating superior operational stability. • • The meltable additive-enabled LMA approach provides a scalable, cost-effective route to strain management, addressing a key bottleneck in perovskite solar cell commercialization.