Efficient and Stable CdSe/CdS/ZnS Quantum Rods-in-Matrix Assembly for White LED Application.

Yujuan Chen,Yixuan Liu,Weishuo Xing,Xinsu Zhang,Jay Guoxu Liu,Chongyu Shen,Shu Xu,Chong Geng,Yangyang Xie

doi:10.3390/nano10020317

Abstract

CdSe/CdS core-shell quantum rods (QRs) are a promising prospect in optoelectronic applications but usually have a relatively low quantum efficiency and stability. Here, we report on an efficient and stable CdSe/CdS/ZnS QRs-in-matrix assembly (QRAs) by growing and embedding CdSe/CdS QRs in ZnS matrices. Structural characterizations show that the CdSe/CdS QRs are encapsulated and interconnected by ZnS in the QRAs structure. The stable ZnS encapsulation renders the CdSe/CdS QRs high quantum efficiency (QE) up to 85%. The QRAs also present high photo- and thermal-stability and can preserve 93% of the initial QE at 100 °C. The QRAs powder presents a light degradation of only 2% under continuous excitation for 100 h, displaying profound potential in optoelectronic applications. White light-emitting diodes (WLEDs) are fabricated by packaging the QRAs powder as phosphor on top of blue GaN chip. The WLED shows high optical performance and light quality.

Highlights

CdSe/CdS dot-in-rod nanocrystals integrate the 0D confined quantum dots (QDs) within 1D quantum rods [1,2,3,4]. This heterostructure endows the CdSe/CdS quantum rods (QRs) with a larger Stokes shift, intense polarized emission, faster radiative decay, and intrinsic charge separation [5,6,7,8]. These unique optical and electrical features make CdSe/CdS QRs promising for optoelectronic applications such as light-harvesting [7], biosensing [4], visible lighting communication [9,10,11], and light-emitting diodes (LEDs) [12,13]
For CdSe/CdS QRs, the CdS rod acts as an efficient absorber for light below 470 nm, and the generated excitons in CdS can transfer to the quantum confined CdSe core and promote emission at longer wavelengths [19,20]
This characteristic is important for lighting and display applications in which the mixed green and red emitting QDs and QRs are excited by blue LEDs [21,22,23]

Summary

Introduction

CdSe/CdS dot-in-rod nanocrystals integrate the 0D confined quantum dots (QDs) within 1D quantum rods [1,2,3,4]. For CdSe/CdS QRs, the CdS rod acts as an efficient absorber for light below 470 nm, and the generated excitons in CdS can transfer to the quantum confined CdSe core and promote emission at longer wavelengths [19,20] This characteristic is important for lighting and display applications in which the mixed green and red emitting QDs and QRs are excited by blue LEDs [21,22,23]. The practical application of CdSe/CdS and CdSe/CdS/ZnS QRs is still limited because of their relatively low quantum efficiency (QE) and stability compared to the “giant” spherical CdSe/CdS/ZnS QDs [26,27] This issue is mainly attributed to the surface defects on CdS, which trap the electrons and induce non-radiative recombination [28,29,30]. White-light LEDs (WLEDs) based on QRAs were further fabricated to verify the high performance of the QRAs in practical optoelectronic applications

Materials

Fabrication of WLEDs with QRs and QRAs

Characterizations

Findings

Conclusions