Dielectric Confinement and Exciton Fine Structure in Lead Halide Perovskite Nanoplatelets.

Amal Ghribi,Laurent Legrand,Kaïs Boujdaria,Maria Chamarro,Thierry Barisien,Rim Ben Aich,Christophe Testelin

doi:10.3390/nano11113054

Abstract

Owing to their flexible chemical synthesis and the ability to shape nanostructures, lead halide perovskites have emerged as high potential materials for optoelectronic devices. Here, we investigate the excitonic band edge states and their energies levels in colloidal inorganic lead halide nanoplatelets, particularly the influence of dielectric effects, in a thin quasi-2D system. We use a model including band offset and dielectric confinements in the presence of Coulomb interaction. Short- and long-range contributions, modified by dielectric effects, are also derived, leading to a full modelization of the exciton fine structure, in cubic, tetragonal and orthorhombic phases. The fine splitting structure, including dark and bright excitonic states, is discussed and compared to recent experimental results, showing the importance of both confinement and dielectric contributions.

Highlights

Two-dimensional colloidal nanostructures, named nanoplatelets (NPLs), have attracted a large interest over the last decade
We focus on the calculation of the excitonic fine structure splitting (FSS) in NPLs made of inorganic cesium lead halide perovskite
We have only reported exciton energies deduced from absorption measurements on CsPbBr3

Summary

Introduction

Two-dimensional colloidal nanostructures, named nanoplatelets (NPLs), have attracted a large interest over the last decade. II–VI semiconductors such as CdSe [2] Such NPLs exhibit strong exciton confinement and outstanding optical and electronic properties for applications, such as a high absorption [3], large exciton binding energies [4], narrow and fast emission lines [5], or large two-photon absorption [6]. The flexible chemical synthesis offers the opportunity to have free-standing nanostructures, adapted to device integration, while controlling the NPL thickness at the atomic layer and suppressing inhomogeneous broadening. Perovskite NPLs with thicknesses of a few monolayers and a very large area can be incorporated in planar electro-optical devices with the advantage of a facile combination with other high-value functional materials and, in particular, with organic semiconductors

Methods

Results

Conclusion