4-(Aminoethyl)pyridine as a Bifunctional Spacer Cation for Efficient and Stable 2D Ruddlesden-Popper Perovskite Solar Cells.

Two-dimensional (2D) Ruddlesden-Popper (RP) perovskites are attractive due to their appealing environmental stability. We demonstrate herein a spacer cation, 4-(aminoethyl)pyridine (4-AEP), for preparation of 2D RP perovskite films. The 4-AEP can not only act as a spacer cation but also coordinate with the Pb ions in PbI with the nitrogen atom on the pyridine ring. High-quality 2D RP perovskite films can thus be formed as the coordination interaction retards the crystallization rate of the 2D RP perovskites. As a result, the solar cell employing the (4-AEP)MAPbI ( = 5) 2D perovskite achieves a power conversion efficiency (PCE) of 11.68% with good air stability, which is much better than the phenylethylamine spacer cation at the same conditions (PCE = 7.95%). This work provides a new idea for designing novel spacer cations toward efficient and stable 2D RP perovskite solar cells.