Thickness-variation-insensitive near-infrared quantum dot LEDs

Wan-Shan Shen; Yang Liu; Luke Grater; So Min Park; Haoyue Wan; Yan-Jun Yu; Jia-Lin Pan; Fan-Cheng Kong; Qi-Sheng Tian; Dong-Ying Zhou; Zeke Liu; Wanli Ma; Baoquan Sun; Sjoerd Hoogland; Ya-Kun Wang; Liang-Sheng Liao

doi:10.1016/j.scib.2023.10.018

Thickness-variation-insensitive near-infrared quantum dot LEDs

Sci Bull (Beijing). 2023 Dec 15;68(23):2954-2961. doi: 10.1016/j.scib.2023.10.018. Epub 2023 Oct 27.

Authors

Affiliations

¹ Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, Suzhou 215123, China.
² Department of Electrical and Computer Engineering, University of Toronto, Toronto M5S 3G4, Canada.
³ Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, Suzhou 215123, China. Electronic address: zkliu@suda.edu.cn.
⁴ Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, Suzhou 215123, China; Department of Electrical and Computer Engineering, University of Toronto, Toronto M5S 3G4, Canada. Electronic address: wangyakun@suda.edu.cn.
⁵ Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, Suzhou 215123, China; Macao Institute of Materials Science and Engineering, Macau University of Science and Technology, Macao 999078, China. Electronic address: lsliao@suda.edu.cn.

PMID: 37919156
DOI: 10.1016/j.scib.2023.10.018

Abstract

In terms of tunable luminescence and high quantum efficiency, colloidal quantum dots (CQDs) are promising semiconductors for constructing near-infrared light-emitting diodes (NIR-LEDs). However, currently available NIR-LEDs are susceptible to variations in the emission layer thickness (EMLT), the highest external quantum efficiency (EQE) decreases to below 50% (relative to peak EQE) when the EMLT varies out of a narrow range of (±30 nm). This is due to the thickness-dependent carrier recombination rate and current density variation, resulting in batch-to-batch EQE fluctuations that limit LED reproducibility. Here we report efficient NIR-LEDs that exhibit EQE variations of less than 15% (relative to the champion EQE) over an EMLT range of 40-220 nm; the highest achievable EQE of ∼11.5% was obtained by encapsulating a 212 nm-thick CQD within a type-I inorganic shell to enhance the radiative recombination in the dots, resulting in a high photoluminescence quantum yield of 80%, and by post-treating the films with a bifunctional linking agent to improve and balance the hole and electron mobilities in the entire film (electron mobility: 8.23 × 10^-3 cm² V^-1 s^-1; hole mobility: 7.0 × 10^-3 cm² V^-1 s^-1). This work presents the first NIR-LEDs that exhibit EMLT-invariant EQE over an EMLT range of 40-220 nm, which represents the highest EQE among reported CQD NIR-LEDs with a QD thickness exceeding 100 nm.

Keywords: Electroluminescence; Light-emitting diodes; Near-infrared; Quantum dots.