Reducing Dielectric Confinement Effect Enhances Carrier Separation in Two‐Dimensional Hybrid Perovskite Photocatalysts
Zhaohui Fang, Guohong Wang, Chen Guan, Jianjun Zhang, Quanjun Xiang
Abstract
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.