Interlayer Interaction Enhancement in Ruddlesden–Popper Perovskite Solar Cells toward High Efficiency and Phase Stability

Ruddlesden–Popper perovskites (RPPs) have attracted intense attention owing to their superior stability. However, the interspace and weak interaction between the inorganic layers inhibits direct charge transfer and brings the phase segregation issue under light illumination. Herein, it is presented that after incorporation of a symmetric cation guanidinium (GA + ) with three amino groups the crystallinity, photoelectronic properties, and stability can be synchronously ameliorated owning to the enhanced interlayer interaction. The new (BA,GA) 2 (MA) 2 Pb 3 I 10 RPP film shows a preferentially vertical orientation and possesses a spatially well-aligned band from the bottom to the top surface, resulting in fast energy transfer. It contributes to a large V oc of 1.25 V with minimized nonradiative loss of 0.14 V and a boosted efficiency of 14.47%. More importantly, the lattice strain in the RPP film can be eliminated due to the medium size of GA +, protecting it from phase segregation even under laser irradiation.