Investigation of anti-solvent induced optical properties change of cesium lead bromide iodide mixed perovskite (CsPbBr3-xIx) quantum dots

Lin Yuan; Robert Patterson; Xiaoming Wen; Zhilong Zhang; Gavin Conibeer; Shujuan Huang

doi:10.1016/j.jcis.2017.06.017

Investigation of anti-solvent induced optical properties change of cesium lead bromide iodide mixed perovskite (CsPbBr_3-xI_x) quantum dots

J Colloid Interface Sci. 2017 Oct 15:504:586-592. doi: 10.1016/j.jcis.2017.06.017. Epub 2017 Jun 7.

Authors

Lin Yuan¹, Robert Patterson², Xiaoming Wen², Zhilong Zhang², Gavin Conibeer², Shujuan Huang³

Affiliations

¹ School of Photovoltaic and Renewable Energy Engineering, The University of New South Wales, Sydney 2052, Australia. Electronic address: lin.yuan2@student.unsw.edu.au.
² School of Photovoltaic and Renewable Energy Engineering, The University of New South Wales, Sydney 2052, Australia.
³ School of Photovoltaic and Renewable Energy Engineering, The University of New South Wales, Sydney 2052, Australia. Electronic address: sj.huang@unsw.edu.au.

PMID: 28609742
DOI: 10.1016/j.jcis.2017.06.017

Abstract

Cesium lead halide (CsPbX₃, X=Cl, Br, I) perovskites are a new material system that has attracted a lot of research focus. Its tunable band gap and better thermal stability than organic lead halide perovskite give it the potential for applications in optoelectronic devices such as light-emitting diodes and solar cells. Here we have synthesized CsPbBr_3-xI_x perovskite quantum dots (QDs) via a solution process, and then have selected three different anti-solvents to purify the product. A significant effect on optical properties of CsPbBr_3-xI_x was found after the centrifugation process. Up to a ∼40nm shift was observed in mixed halide CsPbBr_3-xI_x QDs in both absorbance and PL spectra after purification while there was no obvious change in pure CsPbBr₃ when it was subjected to the same purification steps. XPS analysis shows that the Br:I ratio of the CsPbBr_3-xI_x QDs had changed as a result of exposure to the anti-solvent, causing the change of the band gap and shift of the spectra. It is also shown that iodine can be removed more easily than bromine during the anti-solvent purification. Ab-initio simulations of small CsPbBr_3-xI_x atomic clusters suggest that exposed Cs ions on Cs-terminated facets are the first species to be attacked by hydrophilic molecules, likely dragging halide ions into solution with them to maintain overall charge neutrality in the material. Charge carrier recombination rates were found to be unchanged and all samples maintained a good PL quantum yield which was more than 44%.

Keywords: Anti-solvents; Inorganic perovskite; Quantum dots.