Novel PHA Organic Spacer Increases Interlayer Interactions for High Efficiency in 2D Ruddlesden-Popper CsPbI 3 Solar Cells.

The two-dimensional (2D) Ruddlesden-Popper (RP) CsPbI 3 with hydrophobic organic spacers can significantly improve the environmental and phase stability of photovoltaic devices by suppressing ion migration and inducing steric hindrance. However, due to the multiple-quantum-well structure, these spacer cations lead to weak interactions in 2D RP CsPbI 3 , which seriously affect the carrier transport. Here, a novel N-H-group-rich phenylhydrazine spacer, namely, PHA, was developed for 2D RP CsPbI 3 perovskite solar cells (PSCs). A series of characterizations confirm that the 2D perovskites using PHA spacers enhanced the N-H ··· I hydrogen-bonding interaction between the organic spacer cations and the [PbI 6 ] 4- inorganic layer and accelerated the crystallization rate of the perovskite film, which was beneficial to the preparation of high-quality films with preferred vertical orientation, large grain size, and dense morphology. Meanwhile, the trap state density of the as-prepared 2D RP perovskite films is significantly reduced to enable efficient charge carrier transport. As a result, the (PHA) 2 Cs 4 Pb 5 I 16 PSCs achieved a performance of 16.23% with good environmental stability. This work provides a simple organic spacer selection scheme to realize interaction optimization in 2D RP CsPbI 3 to develop efficient and stable PSCs.