Eliminating Buried Interface Voids for High-Efficiency and Stable Perovskite Solar Cells

Solution-processible efficient perovskite solar cell (PSC) has attracted significant attention due to its potential for low-cost, large-scale production. During the annealing process, the removal of common solvent dimethyl sulfoxide (DMSO) from the wet perovskite films is inefficient due to its strong interaction with precursor lead iodide (PbI₂). Although the trapped DMSO eventually evaporates, the voids formed during its evaporation at the buried interface significantly degrade the final film quality, especially when fabricating large-area modules under ambient conditions. Here, we propose an interface engineering strategy to reduce voids at the buried interface by introducing bridging molecules (1,10-Phenanthroline-4,7-dicarboxylic acid, PDA, and 1,10-Phenanthroline-4-carboxylic acid, PCA). Both molecules contain a 1,10-phenanthroline group which can chelate Pb²⁺ ions via two nitrogen atoms. The strong chelation facilitates the evaporation of DMSO and effectively minimizes the formation of voids at the bottom interface. The resultant regular planar perovskite solar cells achieve a power conversion efficiency of 25.15% for small-area devices (0.04 cm²), and 21.15% for mini-modules (aperture area 18.48 cm²) under simulated AM 1.5G sunlight (100 mW cm^-2). Notably, unencapsulated modules retain over 80% of their initial efficiency after 1,500 h storage in ambient air.