Excitons in metal halide perovskite nanoplatelets: an effective mass description of polaronic, dielectric and quantum confinement effects

Abstract

An effective mass model for excitons confined in metal halide perovskite nanoplatelets is presented. Dielectric screening is weakened by the quasi-2D confinement, as the exciton radius becomes comparable to the polaron one.

Electronic Structure of Biexcitons in Metal Halide Perovskite Nanoplatelets

“…For excitons in halide perovskite crystals, it has been observed experimentally 33 and theoretically. 29 We confirm the same trend in BXs, despite the presence of repulsions.…”

“…Both V i self and V c (r i , r j ) account for dielectric confinement by using quantum well image charges, with inclusion of long-and short-range interactions. Detailed expressions can be found in ref 29. These are based on the Haken potential whose expression in bulk�before including quantum and dielectric confinement� we show next for clarity of exposition.…”

“…Equation 2 constitutes a simple model of Xpolaron interactions, which has been shown to improve estimates of X binding energies in different semiconductors, 30−32 including lead halide perovskites. 21,25,27,29 The Hamiltonian described by eq 1 is solved with a fourparameter variational wave function for the BX ground state:…”

“…The second term is a short-range (Yukawa) one, which starts prevailing at distances r ≲ l i , where the ionic contribution to dielectric screening is lost (ϵ ∞ dominates). Equation constitutes a simple model of X-polaron interactions, which has been shown to improve estimates of X binding energies in different semiconductors, − including lead halide perovskites. ,,, …”

Polaronic Mass Enhancement and Polaronic Excitons in Metal Halide Perovskites

“…For a long time, ionic semiconductors have stayed in the shade of covalent semiconductors (III–V, II–VI), where the impact of the phonons on the exciton energy structure could be neglected (the hydrogen model works very well). However, the recent boom in the field of metal-halide perovskites has brought the discussion of the impact of polaronic effects on the excitonic properties into the spotlight of scientific interest. ,− …”