固液混合态量子点发光二极管的高效率研究

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"高效率固液混合态量子点发光二极管" 这篇论文主要探讨了如何解决量子点（Quantum Dots, QDs）在被整合到固态聚合物基质中用于制造发光二极管（Light-Emitting Diodes, LED）设备时，其量子效率降低的问题，这一现象被称为宿主矩阵效应。研究者提出了一种新的固液混合态量子点LED（QD-LED）设计来应对这一挑战。通常，量子点在液态溶液中能够实现接近100%的高量子产率，这意味着它们在吸收能量后能高效地发出光。然而，当这些量子点被集成到固体聚合物基质中形成LED时，由于与基质的相互作用和限制，量子效率会显著下降。这是因为在固态环境中，量子点的热稳定性和光致发光性能可能会受到不利影响，导致能量损失增加。在该研究中，科研团队采用乙烯末端的聚二甲基硅氧烷（ethylene-PDMS）来构建一个固态交联网络，这种材料能够提供相对稳定的支撑结构。同时，他们使用甲基末端的聚二甲基硅氧烷（methyl-PDMS）保持其液态状态。这种固液混合设计旨在兼顾量子点在液态下的高效率和固态基质的稳定性。通过这种创新设计，固态网络可以支持量子点并保持其结构完整性，而液态部分则允许量子点在一定程度上自由移动，从而优化能量转移和光发射过程。实验结果显示，这种方法有效地缓解了宿主矩阵效应，提高了量子点LED的发光效率，对于未来开发更高效、更稳定的QD-LED器件具有重要意义。此外，这项工作还指出，固液混合态QD-LED的实现对量子点的表面修饰和封装技术提出了新的要求。为了实现最佳的光电器件性能，必须精确控制固态和液态组件的比例以及它们之间的界面特性。这篇论文为解决量子点LED的效率问题提供了一个新颖且有前景的解决方案，对能源节约和新能源技术领域的绿色制造工程研究具有积极的推动作用。同时，它也为量子点材料在固态照明和显示技术的应用开辟了新的途径。

High efficiency solid–liquid hybrid-state quantum

dot light-emitting diodes

JIA-SHENG LI,

1,2

YONG TANG,

ZONG-TAO LI,

1,2,

*LONG-SHI RAO,

XIN-RUI DING,

AND BIN-HAI YU

Engineering Research Center of Green Manufacturing for Energy-Saving and New-Energy Technology, South China University

of Technology, Guangzhou 510640, China

Foshan Nationstar Optoelectronics Company Ltd., Foshan 528000, China

*Corresponding author: meztli@scut.edu.cn

Received 8 August 2018; revised 9 October 2018; accepted 10 October 2018; posted 12 October 2018 (Doc. ID 341874);

published 14 November 2018

Quantum dots (QDs) can achieve high quantum yields close to unity in liquid solutions, whereas they exhibit a

decreased conversion efficiency after being integrated into solid-state polymer matrices for light-emitting diode

(LED) devices, which is called the host matrix effect. In this study, we propose a solid–liquid hybrid-state

QD-LED to solve this issue. The ethylene-terminated polydimethylsiloxane (ethylene-PDMS) is used to establish

a solid-state cross-linked network, whereas the methyl-terminated PDMS (methyl-PDMS) is used in its liquid

state. From a macroscopic level, the cured solid–liquid hybrid-state PDMS (SLHP) composites reach a solid state,

which is stable and flexible enough to be used in LED devices. Compared with LEDs using conventional QD/solid

PDMS composites at equal color conversion efficiency rangin g from 40% to 60%, the luminous flux of LEDs with

QD/SLHP composites is increased by 13.0% using an optimized methyl-PDMS concentration of 85 wt. %.

As a result, high efficiency QD-LEDs using QDs as the only color convertor with luminous efficacy of

89.6 lm/W (0.19 A) were achieved, which show a working stability comparable with that using conventional

solid-state structures at a harsh condition. Consequently, the novel approach shows great potential for achieving

high efficiency and high stability QD-LEDs, which is also compatible with current structures used in illumination

and display applications.

https://doi.org/10.1364/PRJ.6.001107

1. INTRODUCTION

Quantum dots (QDs) exhibit high quantum yields (QYs) and

narrow emission spectra and are easy to produce [1]. Thus, they

show great potential for optoelectronic devices requiring

color conversion functions[2,3 ], such as light-emitting diodes

(LEDs) [4]. Much effort is devoted to improving the QYs of

QDs by optimizing the synthetic methods [5] and band struc-

tures [6]. At present, CdSe/ZnS QDs with core/shell structures

achieve a QY of above 90% [1,7] and have become one of the

most promising color conversion materials to replace conven-

tional rare-earth-based phosphors in LEDs [8,9] for illumina-

tion and display applications. LEDs need packaging processes

[10–12] in which the QDs are sealed in transparent polymer

matrices to protect them from environmental-moisture-

induced oxidation [13]. After the QDs have been fabricated

in oily or water solutions [5,14], they must be transferred to

a polymer matrix before being used in LED packaging to pre-

vent the solution from accelerating the degradation of the LED

chips and other packaging elements, such as the lead frame and

encapsulant [10,15]. However, the conversion efficiency of

large QD quantities in a polymer matrix is far lower than that

in a solution [16] owing to reabsorption loss [17,18], aggrega-

tion-induced quenching [19,20], and improper interactions

with the polymer matrix [21,22], which is also called the

host matrix effect. Thus, the luminous efficacy of QD-LEDs

is much poorer than that of conventional phosphor-based

LEDs [18], thereby suppressing commercial applications of

QD-LEDs.

To improve their optical performance, much effort has

been devoted to the optimization of their polymer matrices

[16,23–27]. For instance, polydimethylsiloxane (PDMS),

which exhibits good flexibility, high transparency, and simple

manufacture, provides good dispersity and compatibility for

oil-soluble QDs and has been widely employed for QD-LED

packaging [13,22,28–32]. Thus far, the luminous efficacy of

LEDs with QD/solid PDMS (SP) composites is still far lower

than that of LEDs with QDs in original solutions [33–35]. The

original liquid-state solution provides a better environment for

dispersed QDs and ensures a high optical LED performance,

which leads to a record performance of 105 lm/W (injection

current of 10 mA) for QD-LEDs using green QDs in the liquid

state as the only color convertor [ 35]. However, this liquid

Research Article

Vol. 6, No. 12 / December 2018 / Photonics Research 1107

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