Homogeneous and inhomogeneous broadening in single perovskite nanocrystals investigated by micro-photoluminescence

Hamid Pashaei Adl,Setatira Gorji,Guillermo Muñoz-Matutano,Raúl I Sánchez-Alarcón,Rafael Abargues,Andrés F Gualdrón-Reyes,Iván Mora-Seró,Juan P Martínez-Pastor

doi:10.1016/j.jlumin.2021.118453

Abstract

Metal halides with perovskite crystalline structure have given rise to efficient optoelectronic and photonic devices. In the present work, we have studied the light emission properties of single CsPbBr3 and CsPbI3 semiconductor perovskite nanocrystals (PNCs), as the basis for a statistical analysis of micro-photoluminescence (micro-PL) spectra measured on tens of them. At room temperature, the linewidth extracted from PL spectra acquired in dense films of these nanocrystals is not very different from that of micro-PL measured in single nanocrystals. This means that the homogeneous linewidth due to exciton-phonon interaction is comparable or larger than the inhomogeneous effect associated to the micro-PL peak energy dispersion due to the nanocrystal size distribution defined by the chemical synthesis of the PNCs. Contrarily, we observe very narrow micro-PL lines in CsPbBr3 and CsPbI3 PNCs at 4 K, in the range of 1–5 meV and 0.1–0.5 meV, respectively, because they are limited by spectral diffusion. Aging of PNCs under ambient conditions has been also studied by micro-PL and a clear reduction of their nanocube edge size in the order of the nm/day is deduced.

Highlights

Semiconductor nanocrystals are crystalline structures with size at the nanoscale (1–100 nm), which possess electronic and optical properties according to their semiconductor condition, in addi tion to a possible quantum confinement effect of carriers/excitons due to size reduction
We have demonstrated that the Full Width at Half Maximum (FWHM) of the PL measured in a dense layer of perovskite nanocrystals (PNCs) is not far from the average value of this magnitude found from micro-PL measured in single nanocrystals, around 68 meV, which is limited by exciton-phonon inter action at room temperature (RT)
Details on synthesis of CsPbBr3 and CsPbI3 PNCs, preparation of samples with dispersed single nanocrystals and experimental micro-PL setups at RT and 4 K are given in section S1 of the Supplementary Info

Summary

Introduction

Semiconductor nanocrystals are crystalline structures with size at the nanoscale (1–100 nm), which possess electronic and optical properties according to their semiconductor condition (bandgap energy, energy band dispersion, absorption coefficient, exciton lifetime, etc.), in addi tion to a possible quantum confinement effect of carriers/excitons due to size reduction. If they proceed from direct bandgap semi conductors, efficient light emitters devices [1], and even quantum light emitters at room temperature (RT) [2], can be developed, among other applications. In CsPbX3 PNCs, the PLQY is greater than 40% [19], with the appropriate treatment, values close to

Results

Discussion

Conclusion