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• Photonics Research
• Vol. 9, Issue 11, 11002132 (2021)
Tingzhu Wu1、2、†, Yue Lin1、2、†, Yu-Ming Huang3、†, Meng Liu1, Konthoujam James Singh3, Wansheng Lin1, Tingwei Lu1, Xi Zheng1, Jianyang Zhou1, Hao-Chung Kuo3、4、5、*, and Zhong Chen1、2、6、*
Author Affiliations
• 1School of Electronic Science and Engineering, Fujian Engineering Research Center for Solid-State Lighting, Xiamen University, Xiamen 361005, China
• 2Fujian Science & Technology Innovation Laboratory for Energy Materials of China, Xiamen 361005, China
• 3Department of Photonics and Graduate Institute of Electro-Optical Engineering, College of Electrical and Computer Engineering, Taiwan Chiao Tung University, Hsinchu 30010, China
• 4Semiconductor Research Center, Hon Hai Research Institute, Taipei 11492, China
• 5e-mail: hckuo@faculty.nctu.edu.tw
• 6e-mail: chenz@xmu.edu.cn
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Abstract

A promising approach for the development of effective full-color displays is to combine blue microLEDs (μLEDs) with color conversion layers. Perovskite nanocrystals (PNCs) are notable for their tolerance to defects and provide excellent photoluminescence quantum yields and high color purity compared to metal chalcogenide quantum dots. The stability of PNCs in ambient conditions and under exposure to blue light can be improved using a $SiO2$ coating. This study proposes a device that could be used for both display and visible light communication (VLC) applications. The semipolar blue μLED array fabricated in this study shows a negligible wavelength shift, indicating a significant reduction in the quantum confined Stark effect. Owing to its shorter carrier lifetime, the semipolar μLED array exhibits an impressive peak 3 dB bandwidth of 655 MHz and a data transmission rate of 1.2 Gb/s corresponding to an injection current of 200 mA. The PNC–μLED device assembled from a semipolar μLED array with PNCs demonstrates high color stability and wide color-gamut features, achieving 127.23% and 95.00% of the National Television Standards Committee standard and Rec. 2020 on the CIE 1931 color diagram, respectively. These results suggest that the proposed PNC–μLED device is suitable for both display-related and VLC applications.

1. INTRODUCTION

Owing to their versatility and tunability, microLEDs (μLEDs) with sizes less than 50 μm are considered integral components of next-generation display technology and are able to satisfy the demands of sophisticated devices, such as cellphones, smart watches, virtual reality, microprojectors, and ultra-high-definition TVs [1,2]. Over the past decade, the number of commercially available μLED displays has grown significantly, as manufacturers seek to capitalize on the success of this technology [3]. μLEDs have the potential to surpass organic LEDs by providing displays with high contrast, a wide color gamut, high efficiency, and a wide viewing angle, which are additional to the prospect of translucent and versatile displays [4]. Huang Chen et al. demonstrated a hybrid quantum dot–nanoring–μLED that exhibited a color gamut of approximately 104.8% of the National Television Standards Committee (NTSC) standard and 78.2% of Rec. 2020 [4,5]. Huang et al. achieved a record high external quantum efficiency (EQE) for green and blue QLEDs, and the devices exhibited a record 90% coverage of Rec. 2020, which exhibits lifetimes longer than 100,000 and 280,000 h for green and red QLEDs for ultra-high definition displays, respectively [5]. Full-color displays can be achieved via mass transfer processes using RGB μLEDs. However, this approach has several drawbacks, such as low efficiency caused by the so-called “green-gap” originating from green μLEDs and nonradiative recombination at the surface for red μLEDs owing to the use of AlGaInP as the active region material [6]. A further problem for red μLEDs is that the EQE decreases when the pixel size decreases [7]. To address these problems, blue μLEDs can be integrated with color converters, such as yellow-emitting phosphors or nanocrystals (NCs) that emit red and green light, to achieve higher quality full-color displays [8]. Lin et al. successfully fabricated high-luminance efficiency and a wide color gamut for an NC-based solid and hybrid-type WLED device, which exhibits a higher efficiency (51 lm/W), a wide color gamut (122% of NTSC and 91% of Rec. 2020), and an efficiency decay of approximately 12% during a 200 h reliability test [9]. However, phosphors are not suitable for microdisplay technology because of their large particle size [10]. In contrast, NCs offer several compelling features, including the quantum confinement effect (specifically for quantum dots), a narrow emission spectrum, high quantum yield, and low manufacturing costs, which makes them an attractive alternative for phosphors in full-color displays [11].