Engineering Auger recombination in colloidal quantum dots via dielectric screening

Xiaoqi Hou,Jianhai Zhou,Liping Chen,Lin-Wang Wang,Junliang Ma,Xiaogang Peng,Xuewen Chen,Linjun Wang,Haiyan Qin,Jun Kang

doi:10.1038/s41467-019-09737-2

Abstract

Auger recombination is the main non-radiative decay pathway for multi-carrier states of colloidal quantum dots, which affects performance of most of their optical and optoelectronic applications. Outstanding single-exciton properties of CdSe/CdS core/shell quantum dots enable us to simultaneously study the two basic types of Auger recombination channels—negative trion and positive trion channels. Though Auger rates of positive trion are regarded to be much faster than that of negative trion for II-VI quantum dots in literature, our experiments find the two rates can be inverted for certain core/shell geometries. This is confirmed by theoretical calculations as a result of geometry-dependent dielectric screening. By varying the core/shell geometry, both types of Auger rates can be independently tuned for ~ 1 order of magnitude. Experimental and theoretical findings shed new light on designing quantum dots with necessary Auger recombination characteristics for high-power light-emitting-diodes, lasers, single-molecular tracking, super-resolution microscope, and advanced quantum light sources.

Highlights

Due to Auger non-radiative recombination of multicarrier states, short gain lifetime in quantum dots (QDs) lasing[6,8] and efficiency roll-off in QD-based light-emitting-diodes[10,11] are frequently observed
For commonly studied CdSe/CdS core/shell[25,26,31], CdSe/gradient-shell[25,26], and other II–IV QDs28, Auger recombination of positive trion has been regarded to be always dominating that of the corresponding negative trion
For certain geometric structures, Auger recombination of positive trion can become significantly slower than that of the corresponding negative trion

Summary

Introduction

Due to Auger non-radiative recombination of multicarrier states, short gain lifetime in QD lasing[6,8] and efficiency roll-off in QD-based light-emitting-diodes[10,11] are frequently observed. Photoluminescence blinking of QDs can be applied for super-resolution microscopy[17], and Auger is beneficial for purity of QD-based single-photon source powered by either photo-excitation[18,19,20] or electro-excitation[21]. These facts suggest that the challenge is how to tune Auger non-radiative recombination of QDs in a controllable manner. Synthetic chemistry of QDs recently makes ideal single-exciton properties be accessible for the most developed CdSe/CdS core/ shell QDs14,22,23, but synthetic control of multi-carrier states remains in its infancy primarily because of poor understanding of Auger non-radiative recombination in QDs24. For commonly studied CdSe/CdS core/shell[25,26,31], CdSe/gradient-shell[25,26], and other II–IV QDs28, Auger recombination of positive trion has been regarded to be always dominating that of the corresponding negative trion

Methods

Results

Conclusion