Applications of lasers:A promising route toward low-cost fabrication of high-efficiency full-color micro-LED displays

Micro-light-emitting diodes(micro-LEDs)with outstanding performance are promising candidates for next-generation displays.To achieve the application of high-resolution displays such as meta-displays,virtual reality,and wearable electronics,the size of LEDs must be reduced to the micro-scale.Thus,traditional technology cannot meet the demand during the processing of micro-LEDs.Recently,lasers with short-duration pulses have attracted attention because of their unique advantages during micro-LED processing such as noncontact processing,adjustable energy and speed of the laser beam,no cutting force acting on the devices,high efficiency,and low cost.Herein,we review the techniques and principles of laser-based technologies for micro-LED displays,including chip dicing,geometry shaping,annealing,laserassisted bonding,laser lift-off,defect detection,laser repair,mass transfer,and optimization of quantum dot color conversion films.Moreover,the future prospects and challenges of laser-based techniques for micro-LED displays are discussed.

Investigation of Quantum Dot Color Filter Micro-LED Display

In this work,we present the investigation of the quantum dot color filter(QDCF)micro-light emitting diode(micro-LED)display.Green and red quantum dot photoresist(QDPR)materials are patterned into a pixelated array and precisely bonded with an all-blue micro-light emitting diode(micro-LED)substrate,forming a red,green,and blue(RGB)full color display through color conversion.A few factors that influence the achievable color gamut are further investigated.The resulting 1.1-inch 228-pixels per inch(ppi)display demo shows the good performance.The findings in this paper pave a way to the future industrialization of the micro-LED display.

高调制带宽下的氮化镓Micro-LED LiFi光通信系统的设计与实现

本研究旨在探究高调制带宽下的氮化Micro-LED LiFi光通信系统在高调制带宽下的技术应用,首先,阐述了高调制带宽下的氮化Micro-LED LiFi系统原理,分析了其基于微小发光二极管的高速光通信的可行性。接着,完善了系统硬件设计的选型与优化,在系统软件设计层面,采用了先进的信号处理和调制解调技术,实现了高速数据传输和低误码率。最后,完成了系统实现与测试,搭建了实验平台进行了性能评估。结果表明,通过优化硬件和软件设计,系统成功实现了高传输率,在不同距离和角度下进行了功能测试,验证了系统的安全可靠性,为系统性能的进一步提升奠定了良好的技术基础。

240 nm AlGaN-based deep ultraviolet micro-LEDs:size effect versus edge effect

240 nm AlGaN-based micro-LEDs with different sizes are designed and fabricated.Then,the external quantum efficiency(EQE)and light extraction efficiency(LEE)are systematically investigated by comparing size and edge effects.Here,it is revealed that the peak optical output power increases by 81.83%with the size shrinking from 50.0 to 25.0μm.Thereinto,the LEE increases by 26.21%and the LEE enhancement mainly comes from the sidewall light extraction.Most notably,transversemagnetic(TM)mode light intensifies faster as the size shrinks due to the tilted mesa side-wall and Al reflector design.However,when it turns to 12.5μm sized micro-LEDs,the output power is lower than 25.0μm sized ones.The underlying mechanism is that even though protected by SiO2 passivation,the edge effect which leads to current leakage and Shockley-Read-Hall(SRH)recombination deteriorates rapidly with the size further shrinking.Moreover,the ratio of the p-contact area to mesa area is much lower,which deteriorates the p-type current spreading at the mesa edge.These findings show a role of thumb for the design of high efficiency micro-LEDs with wavelength below 250 nm,which will pave the way for wide applications of deep ultraviolet(DUV)micro-LEDs.

Flexible high-resolution micro-LED display device with integrations of transparent,conductive,and highly elastic hydrogel

Computer vision techniques are real-time,immersive,and perceptual human-computer interaction technology.Excellent display effect,dynamic surface flexibility,and safe bio-adhesion are essential for various human–computer interaction applications,such as metaverse interfaces,skin-like sensors,and optoelectronic medical devices.However,realizing the flexible matching of inorganic optoelectronic devices and organisms remains a grand challenge for current display technologies.Here,we proposed a novel strategy by combining the optoelectronic advantages of inorganic micro light emitting diode(micro-LED)display and the extraordinary mechanical/biological compatibility of organic materials to overcome this challenge.A highly elastic(greater than 2000%strain),highly transparent(94%visible light transmittance),biocompatible conductive hydrogel composite electrode layer was fabricated.For the first time,we realized the on-chip electrical interconnection of 4900 LED units to form a blue-green light display patch with high resolution(264 PPI),low power consumption(4.4 mW)and adaptive surface attachment.This work demonstrates an integrated scheme and potential applications of flexible high-resolution microdisplays,such as wearable fullcolor micro-LED smart curved display devices and conformable biomedical monitoring systems.

晶圆级Micro-LED芯片检测技术研究进展

随着微型氮化镓(GaN)发光二极管(LED)制造工艺的不断进步,Micro-LED显示有望成为新一代显示技术并在近眼显示、大尺寸高清显示器件、柔性屏幕等领域大放异彩。在Micro-LED显示众多技术环节中,晶圆级Micro-LED芯片的检测是实现坏点拦截,提升显示屏良品率、降低整机制造成本的关键环节。针对大数量(百万数量级)、小尺寸(<50μm)的晶圆级Micro-LED芯片阵列,现有的电学检测手段存在检测效率低、成本高等缺点。因此,提高检测效率、提升检测准确度、降低检测成本是晶圆级Micro-LED检测技术的发展趋势。本文首先介绍了晶圆级Micro-LED芯片检测时所需要检测的几个指标,其次详细介绍并分析了现有的或已经提出的检测手段,最后对晶圆级Micro-LED芯片检测技术进行总结并展望了未来技术发展方向。

Micro-LED的侧壁损伤以及光学特性

GaN基微型发光二极管(Micro-LED)作为新型显示技术有着广泛的应用前景,在近些年得到了快速的发展。但随着尺寸的降低,Micro-LED的发光效率急剧降低,主要是由于侧壁损伤的影响。本文通过光刻工艺和电感耦合等离子体(ICP)刻蚀制作了5、10、20μm等不同尺寸的Micro-LED结构,分析了刻蚀对Micro-LED带来的台面物理损伤及杂质元素富集的影响,并采用20%浓度四甲基氢氧化铵(TMAH)修复侧壁损伤,采用阴极荧光(CL)分析钝化处理前后Micro-LED的光学特性。结果表明,随着尺寸的降低,侧壁损伤的影响越加严重,采取TMAH钝化工艺能够对侧壁进行有效的修复,提升Micro-LED的发光强度与发光均匀性。

Review of a direct epitaxial approach to achieving micro-LEDs

There is a significantly increasing demand of developing augmented reality and virtual reality(AR and VR) devices,where micro-LEDs(μLEDs) with a dimension of ≤ 5 μm are the key elements. Typically, μLEDs are fabricated by dry-etching technologies, unavoidably leading to a severe degradation in optical performance as a result of dry-etching induced damages. This becomes a particularly severe issue when the dimension of LEDs is ≤ 10 μm. In order to address the fundamental challenge, the Sheffield team has proposed and then developed a direct epitaxial approach to achievingμLEDs, where the dry-etching technologies for the formation of μLED mesas are not needed anymore. This paper provides a review on this technology and then demonstrates a number of monolithically integrated devices on a single chip using this technology.

极性相反结构的micro-LED和OLED混合集成显示器件的驱动

本文提出一种由OLED和micro-LED反向并联组成的AC全彩显示器件。该器件由二者按相反极性结构并联而成,能改善传统器件不同颜色子像素之间的亮度和光效不均匀等问题,兼具高发光效率、高像素密度和长时间工作寿命等优点。同时,本文提出了一种与之适配的反向并联显示器件专用驱动方案。新型显示器件能够改善传统单一元素显示器件的亮度和光效不均匀性,显示方案的提出能够解决传统驱动方案不适配AC显示器件反向并联结构的驱动问题。

Characteristics and techniques of GaN-based micro-LEDs for application in next-generation display

Due to the excellent optoelectronic properties,fast response time,outstanding power efficiency and high stability,micro-LED plays an increasingly important role in the new generation of display technology compared with LCD and OLED display.This paper mainly introduces the preparation methods of the GaN-based micro-LED array,the optoelectronic characteristics,and several key technologies to achieve full-color display,such as transfer printing,color conversion by quantum dot and local strain engineering.

Micro-LED显示的发展与技术研究

Micro-LED是新时代LED领域发展的必然趋势,同时也是未来全球显示设备领域发展的重要内容之一,因此,未来需对Micro-LED显示的发展和技术的研究予以重视。文章主要针对Micro-LED显示的发展现状和技术进行分析,并对Micro-LED显示的未来发展加以阐述和探讨。

Micro-LED显示驱动IC技术的应用研究

在电子信息化进程的持续推进下,Micro-LED显示技术应运而生,该技术具备较多优势,包括功耗低、分辨率高、微型化和响应速度快等,已被广泛应用于可见光通信、医疗探测、空间显示等领域。驱动IC在Micro-LED显示技术中处于重要地位,对Micro-LED的发展意义重大。基于此,文章分析Micro-LED的显示原理和结构,阐述其技术优势,并对Micro-LED显示技术中驱动IC的应用进行了研究,以供参考。

Micro-LED器件:从极性c面到非极性或半极性的发展趋势

氮化镓作为第三代照明器件材料相较于第一代硅与第二代砷化镓在性能上有了很大提高,基于氮化镓的MicroLED器件也愈发被人们所关注。然而由于在传统c面上生长的LED其自身所固有的一些缺陷往往在实际应用中发射效率不高,如存在量子限制斯塔克效应、绿色间隙、载流子传输等问题。基于非极性或半极性的LED没有极化电场,具有较强的内量子效率,电子和空穴复合机率大等优点,对非极性和半极性Micro-LED器件的研究与应用引起了人们很大的兴趣。本文对非极性和半极性Micro-LED器件研究现状进行综述。首先从量子限制斯托克效应、绿色间隙、载流子传输、效率下降4个方面介绍了非极性和半极性氮化镓基材料的优势。接着针对缺陷位错、增加光提取效率与在不同电流密度下实现全彩显示等问题,介绍了芯片成形、图案刻蚀与阵列这3种技术,最后对Micro-LED作为下一代显示引领者进行了展望。希望对Micro-LED今后的研究有所帮助。

超微型Micro-LED投影显示光学引擎设计

随着微米级像素尺寸的微型自发光二极管(Micro-LED,μLED)的出现和发展,采用μLED作为光源和像源的超微型投影光学引擎成为了可能,其极大简化了传统投影显示光学引擎的结构。本文提出了一种基于μLED的超微型投影光学引擎,基于现有3.302 mm(0.13 in)的μLED显示芯片设计了高像质的微型投影镜头。针对μLED的光分布特性,优化μLED发散角度与微投影镜头的光瞳匹配,有效提升了μLED微投影光学系统的光能利用率。结果表明,所设计的μLED微投影显示光学引擎体积仅有18.35 mm^(3),投影镜头中心视场的MTF值在截止频率处超过0.57。该μLED微投影显示光学引擎较好地实现了系统体积与成像像质的均衡,未来在AR/VR等近眼显示设备上具有广泛的应用前景。

Alleviating the crosstalk effect via a fine-moulded light-blocking matrix for colour-converted micro-LED display with a 122% NTSC gamut

One of the major challenges when fabricating high gamut colour-converted micro-light-emitting diodes(LEDs)displays is severe crosstalk effect among adjacent pixels because of the wide view-angle feature of micro-LED chips.In this study,potential factors that contribute to the crosstalk effect were systematically simulated.We observed that precisely filling the space between each micro-LED chip with a light blocking matrix(LBM)can be a promising solution to alleviate this risk.After careful investigations,a press-assisted moulding technique was demonstrated to be an effective approach of fabricating the LBM.Nevertheless,experimental observations further revealed that residual black LBM on the surface of micro-LEDs severely reduces the brightness,thereby compromising the display performance.This problem was successfully addressed by employing a plasma etching technique to efficiently extract the trapped light.Eventually,a top-emitting blue micro-LED-based backlight fine-moulded with a black LBM was developed and combined with red and green quantum dot colour-conversion layers for full-colour display.The colour gamut of our manufactured display prototype can cover as high as 122%that of the National Television Standards Committee.

一种用于Micro-LED的新型PWM像素电路设计

目前,市场上的微型发光二极管(Micro-Light Emitting Diode. Micro-LED)的像素电路广泛使用的是有机发光半导体(OLED)上所使用的脉冲幅度调制(PAM)像素电路。PAM会导致Micro-LED的色移现象,不适用于Micro-LED。脉冲宽度调制(PWM)采用电压占空比控制LED的亮度,其电流是固定的,可以解决色移问题。因此,文章开发了一种用于Micro-LED的新型PWM像素电路。开发的像素电路可以降低功耗,实现60 Hz的驱动电路频率和120 Hz的LED照明频率。

Dynamic interactive bitwise meta-holography with ultra-high computational and display frame rates

Interactive holography offers unmatched levels of immersion and user engagement in the field of future display.Despite of the substantial progress has been made in dynamic meta-holography,the realization of real-time,highly smooth interactive holography remains a significant challenge due to the computational and display frame rate limitations.In this study,we introduced a dynamic interactive bitwise meta-holography with ultra-high computational and display frame rates.To our knowledge,this is the first reported practical dynamic interactive metasurface holographic system.We spa-tially divided the metasurface device into multiple distinct channels,each projecting a reconstructed sub-pattern.The switching states of these channels were mapped to bitwise operations on a set of bit values,which avoids complex holo-gram computations,enabling an ultra-high computational frame rate.Our approach achieves a computational frame rate of 800 kHz and a display frame rate of 23 kHz on a low-power Raspberry Pi computational platform.According to this methodology,we demonstrated an interactive dynamic holographic Tetris game system that allows interactive gameplay,color display,and on-the-fly hologram creation.Our technology presents an inspiration for advanced dynamic meta-holography,which is promising for a broad range of applications including advanced human-computer interaction,real-time 3D visualization,and next-generation virtual and augmented reality systems.

Flexible perovskite light-emitting diodes for display applications and beyond

The flexible perovskite light-emitting diodes(FPeLEDs),which can be expediently integrated to portable and wearable devices,have shown great potential in various applications.The FPeLEDs inherit the unique optical properties of metal halide perovskites,such as tunable bandgap,narrow emission linewidth,high photoluminescence quantum yield,and particularly,the soft nature of lattice.At present,substantial efforts have been made for FPeLEDs with encouraging external quantum efficiency(EQE)of 24.5%.Herein,we summarize the recent progress in FPeLEDs,focusing on the strategy developed for perovskite emission layers and flexible electrodes to facilitate the optoelectrical and mechanical performance.In addition,we present relevant applications of FPeLEDs in displays and beyond.Finally,perspective toward the future development and applications of flexible PeLEDs are also discussed.

Non-volatile dynamically switchable color display via chalcogenide stepwise cavity resonators

High-resolution multi-color printing relies upon pixelated optical nanostructures,which is crucial to promote color display by producing nonbleaching colors,yet requires simplicity in fabrication and dynamic switching.Antimony trisulfide(Sb_(2)S_(3))is a newly rising chalcogenide material that possesses prompt and significant transition of its optical characteristics in the visible region between amorphous and crystalline phases,which holds the key to color-varying devices.Herein,we proposed a dynamically switchable color printing method using Sb_(2)S_(3)-based stepwise pixelated Fabry-Pérot(FP)cavities with various cavity lengths.The device was fabricated by employing a direct laser patterning that is a less timeconsuming,more approachable,and low-cost technique.As switching the state of Sb_(2)S_(3) between amorphous and crystalline,the multi-color of stepwise pixelated FP cavities can be actively changed.The color variation is due to the profound change in the refractive index of Sb_(2)S_(3) over the visible spectrum during its phase transition.Moreover,we directly fabricated sub-50 nm nano-grating on ultrathin Sb_(2)S_(3) laminate via microsphere 800-nm femtosecond laser irradiation in far field.The minimum feature size can be further decreased down to~45 nm(λ/17)by varying the thickness of Sb_(2)S_(3) film.Ultrafast switchable Sb_(2)S_(3) photonic devices can take one step toward the next generation of inkless erasable papers or displays and enable information encryption,camouflaging surfaces,anticounterfeiting,etc.Importantly,our work explores the prospects of rapid and rewritable fabrication of periodic structures with nano-scale resolution and can serve as a guideline for further development of chalcogenide-based photonics components.

Micro-LED技术和产业化研究进展

基于Micro-LED技术发展趋势和新特点,从产线建设和战略合作等角度,对我国Micro-LED产业化进展进行了总结,指出发展面临的瓶颈主要有外延生长、巨量转移、有源背板驱动和彩色化等几大部分,这些部分之间存在不同又相互联系,各部分紧密合作,协同攻克技术瓶颈将是推动Micro-LED技术突破和产业化发展的重要手段。在超大尺寸应用领域和小尺寸应用领域,技术开发和系统集成创新仍然是重要的突破路径,在此过程中,材料和设备的进步也将为MicroLED的大规模量产提供助力。