Hydrogen bond enables highly efficient and stable two-dimensional perovskite solar cells based on 4-pyridine-ethylamine

Most of present 2D perovskites are based on the insulated butylamine or phenylethylamine as the spacing ammonium cation, which require good orientation to improve charge transport. Here, we report a novel 2D perovskite (PyEA)2MAn-1PbnI3n+1 (n = 1–9) based on methylammonium (MA) and a new spacing ammonium of 4-Pyridine-ethyl ammonium (PyEA) cations. Considering the absorption of perovskite films, we choose a high n value of 9 to establish a 2D perovskite system of (PyEA)2MA8Pb9I28 with a bandgap of 1.65 eV as the active layer. The morphology of (PyEA)2MA8Pb9I28 film is improved by using an additive of methylammonium thiocyanate (MASCN), which leads to a highly efficient inverted solar cells with a planar structure of ITO/PEDOT: PSS/(PyEA)2MA8Pb9I28/PC61BM/BCP/Ag. An optimized efficiency of 9.05% is achieved. By virtue of the stable 2D perovskites, the unencapsulated device retains 50% efficiency after 7 days restored in air with a humidity of 55 ± 5%, indicating excellent stability against moisture and oxygen. The high efficiency and good stability are attributed to the improved intermolecular interaction among PyEA molecules via hydrogen bond, which enables the charge transport between inorganic slabs in 2D perovskite. This work provides a new strategy to construct 2D perovskite for highly efficient and stable perovskite solar cells via hydrogen bond.