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

By converting the traditional solid–solid contact to solid–liquid contact, the buried interface of perovskite film is healed to release tensile strain and suppress halide segregation, which universally improves the efficiency and stability of a PSC. [Display omitted] •A universal liquid buried interface is fabricated to replace traditional solid–solid interface.•The weak van der Waals interaction releases the tensile strain.•A champion efficiency of 11.13 % and 14.05 % is achieved for CsPbIBr2 and CsPbI2Br PSCs.•Suppressed halide segregation significantly improves the photostability of PSC. 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.