Dielectric Engineering of 2D Organic–Inorganic Hybrid Perovskites

Abstract

Manipulating excitons in semiconductors has driven the evolution of today's optoelectronic and photovoltaic devices. Engineering the dielectric constant, a key parameter that is highly associated with the Coulomb force of excitons, has recently emerged as a fresh avenue to regulate excitons from the root. Unlike three-dimensional (3D) bulk semiconductors featuring uniformly distributed dielectric constants, the dielectric constants of two-dimensional (2D) layered semiconductors exhibit spatial variability. Particularly, organic−inorganic hybrid perovskites (OIHPs) assembled with alternating organic and inorganic layers show a cyclic variation in the dielectric property, which substantially impacts exciton dynamics, including recombination and separation, offering an opportunity for the regulation of exciton-related physical attributes by dielectric engineering and the cutting-edge applications thereof. This Review documents the recent advances in the rational design of organic and inorganic constituents of 2D OIHPs for dielectric engineering. We show that dielectrically engineered OIHPs are pivotal in driving the advancements in optoelectrical and photovoltaic applications.

Photoexcited charge-carrier transport in monolayer and bulk bismuth oxyiodide: the impact of the polaronic effect and deep-level defects

“…This can be partially explained by the presence of quantum and dielectric confinement effects in the quantum structures of 2D LHPs. These produce stable excitons and lead to inefficient charge separation and collection [49][50][51], as well as strong carrier-phonon scattering mechanisms [52]. This issue has been a subject of ongoing investigations in the scientific community.…”

Optoelectronic insights of lead-free layered halide perovskites

“…When a material is exposed to a static electric field, its long-range charge distribution is significantly influenced by both the coulombic attraction between opposite charge centers, and the electric polarization field ( P ) within the material, where P = χ e ε 0 E 0 ( ε 0 : vacuum dielectric constant, χ e : electric susceptibility, E 0 : vacuum electric field). 25 The relative permittivity, or relative dielectric constant ( ε r ) is a measure of the degree of polarization in bulk dielectrics, and is expressed as ε r = 1 + χ e . In halide perovskites, the excitons are bound by coulombic force, F = − e 2 /4π ε 0 ε r r 2 where, e : electronic charge, and r : distance between electrons and holes.…”

“…2b ). 25,27 Consequently, these factors exert influence over the E b values. The lower dimensional perovskites/hybrid halides (0D, 1D) typically display higher E b , which is advantageous for PL properties but unfavourable for optoelectronic devices.…”

Decoupling interlayer spacing and cation dipole on exciton binding energy in layered halide perovskites

“…15 An alternative and emerging strategy to mitigate the confinement issue in LHPs is dielectric engineering. 16 Passarelli et al reduced Eb of naphthalene-based layered perovskites from 400 meV to 230 meV by using electron-accepting organic dopant to create more polarizable environment and effectively increase the electrostatic screening of exciton. 17 Similarly, Smith et al effectively reduced Eb by incorporating iodine or bromine into (C6H13NH3)2PbI4.…”