Reducing Dielectric Confinement Effect Enhances Carrier Separation in Two‐Dimensional Hybrid Perovskite Photocatalysts

Abstract Two‐dimensional organic–inorganic hybrid perovskites (OIHPs) with alternating structure of the organic and inorganic layers have a natural quantum well structure. The difference of dielectric constants between organic and inorganic layers in this structure results in the enhancement of dielectric confinement effect, which exhibits a large exciton binding energy and hinders the separation of electron‐hole pairs. Herein, a strategy to reduce the dielectric confinement effect by narrowing the dielectric difference between organic amine molecule and [PbBr 6 ] 4− octahedron is put forward. The Ethanolamine (EOA) contains hydroxyl groups, resulting in the positive and negative charge centers of O and H non‐overlapping, which generated a larger polarity and dielectric constant. The reduced dielectric constant produces a smaller exciton binding energy (71.03 meV) of (C 2 H 7 NO) 2 PbBr 4 ((EOA) 2 PbBr 4 ) than (C 8 H 11 N) 2 PbBr 4 ((PEA) 2 PbBr 4 (156.07 meV), and promotes the dissociation of electrons and holes. The increasing of lifetime of photogenerated carrier in (EOA) 2 PbBr 4 are proved by femtosecond transient absorption spectra. Density functional theory (DFT) calculations have also indicated that the small energy shift of the total density of states (DOS) between the C/H/N and the Pb/Br in (EOA) 2 PbBr 4 favors the separation of electrons and holes. In addition, this work demonstrates the application of (PEA) 2 PbBr 4 and (EOA) 2 PbBr 4 in the field of photocatalytic CO 2 reduction.