Giant Stokes shifts in AgInS$_2$ nanocrystals with trapped charge carriers

TL;DR

This paper presents a comprehensive theoretical model explaining the giant Stokes shifts in AgInS$_2$ nanocrystals by integrating electron-electron interactions, electron-phonon coupling, and defect-induced hole trapping, aligning well with experimental data.

Contribution

It introduces a unified theoretical framework combining multiple mechanisms to explain the giant Stokes shifts in AgInS$_2$ nanocrystals, which was not previously achieved.

Findings

The model accurately predicts the magnitude of the Stokes shift.

Photoluminescence arises from recombination of a non-trapped electron with a trapped hole.

Theoretical results closely match recent experimental observations.

Abstract

Nanocrystals of AgInS$_2$ demonstrate giant Stokes shifts ~ 1 eV, the nature of which is still not clearly understood. We propose a theoretical model of this phenomenon bringing together several different mechanisms previously considered only separately. We take into account the contribution of electron-electron interaction with the hybrid density functional theory, as well as the renormalization of energy spectrum due to the electron-phonon coupling. Furthermore, we consider the presence of at least one point defect responsible for hole trapping and the formation of a localized polaron state. Our numerical simulations show that photoluminescence due to the recombination of a non-trapped electron and a trapped hole results in the giant Stokes shift in AgInS$_2$ nanocrystal, which is in close agreement with the recent experimental results.