Liquid buried interface to slide lattice and heal defects in inorganic perovskite solar cells

The residual tensile strain, which is induced by lattice and thermal expansion coefficient difference between upper perovskite film and underlying charge transporting layer, significantly deteriorates the power conversion efficiency (PCE) and stability of a halide perovskite solar cell (PSC). To overcome this technical bottleneck, herein, we propose a universal liquid buried interface (LBI) by introducing a low melting-point small molecule to replace traditional solid-solid interface. Arising from the movability upon solid-to-liquid phase conversion, LBI plays a role of "lubricant" to effectively free the soft perovskite lattice shrinkage or expansion rather than anchoring onto the substrate, leading to the reduced defects due to the healing of strained lattice. Finally, the inorganic CsPbIBr₂ PSC and CsPbI₂Br cell achieve the best PCEs of 11.13 % and 14.05 %, respectively, and the photo-stability is improved by 33.3-fold because of the suppressed halide segregation. This work provides new insights on the LBI for making high-efficiency and stable PSC platforms.