microLED

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microLED, also known as micro-LED, mLED or µLED, is an emerging flat-panel display technology. microLED displays consist of arrays of microscopic LEDs forming the individual pixel elements. When compared with widespread LCD technology, microLED displays offer better contrast, response times, and energy efficiency.

Along with OLEDs, microLEDs are primarily aimed at small, low-energy devices such as smartwatches and smartphones. OLED and microLED both offer greatly reduced energy requirements when compared to conventional LCD systems while also offering an infinite contrast ratio. Unlike OLED, microLED is based on conventional gallium nitride (GaN) LED technology, which offers far higher total brightness than OLED produces, as much as 30 times, as well as higher efficiency in terms of lux/W and thus lower power consumption than OLED. OLED also suffers from screen burn-in, while microLED does not, but microLED displays cannot be made flexible or transparent like OLED displays can.

As of 2019, microLED displays have not been mass-produced, though Sony and Samsung sell microLED video walls, and Luumii mass produces microLED lighting.[1][2][3] LG, Tianma, PlayNitride,TCL/CSoT and Plessey Semiconductors Ltd have demonstrated prototypes.[4][5][6][7][8][9]

Research[edit]

Inorganic semiconductor microLED (µLED) technology[10][11][12][13] was first invented in 2000 by the research group of Hongxing Jiang and Jingyu Lin of Texas Tech University while they were at Kansas State University. Following their first report of electrical injection microLEDs based on Indium gallium nitride (InGaN) semiconductors, several groups have quickly engaged in pursuing this concept.[14][15] Many related potential applications have been identified. Various on-chip connection schemes of microLED pixel arrays have been employed allowing for the development of single-chip high voltage DC/AC-LEDs[16][17][18][19][20][21][22] to address the compatibility issue between the high voltage electrical infrastructure and low voltage operation nature of LEDs and high brightness self-emissive microdisplays.[23][24]

The microLED array has also been explored as a light source for optogenetics applications[25][26] and for visible light communications.[27]

Early InGaN based microLED arrays and microdisplays were primarily passively driven. The first actively driven video-capable self-emissive InGaN microLED microdisplay in VGA format (640 x 480 pixels, each 12 microns in size with 15 microns between them) possessing low voltage requirements was realized in 2011 via a hybrid complementary metal-oxide semiconductor (CMOS) and integrated circuit (IC) hybrid assembly.[28][29]

Commercialization[edit]

microLEDs are considered to have innate potential performance advantages over LCD displays, including lower latency, higher contrast ratio, and greater color saturation, plus intrinsic self-illumination and better efficiency. As of 2016, technological and production barriers have prevented commercialization.[30]

As of 2016 a number of different technologies were under active research for the assembling of individual (pixel, or pixel group) LEDs on a substrate. These include chip bonding of microLED chips onto a substrate, considered to have potential for large displays; wafer production methods using etching to produce an LED array followed by bonding to an IC ; and wafer production methods using an intermediate temporary thin film to transfer the LED array to a substrate.

Sony launched a 55 inch "Crystal LED Display" in 2012 with 1920x1080 resolution, as a demonstrator product.[30] Sony announced its CLEDIS (Crystal LED Integrated Structure) brand which used surface mounted LEDs for large display production.[31] As of August 2019, Sony offers CLEDIS in 146", 182" and 219" displays.[32] On September 12, 2019, Sony announced Crystal LED availability to consumers ranging from 1080p 110" to 16K 790" displays.[33]

Samsung demonstrated a 146" microLED display called The Wall at CES 2018.[34] In July 2018, Samsung announced plans on bringing a 4K microLED TV to consumer market in 2019.[35] At CES 2019, Samsung demonstrated a 75" 4K microLED display and 219" 6K microLED display.[36] On June 12 at InfoComm 2019, Samsung announced the global launch of The Wall Luxury microLED display configurable from 73” in 2K to 292” in 8K.[37] On October 4, 2019, Samsung announced that the The Wall Luxury microLED display shipments had begun.[38]

In March 2018, Bloomberg reported Apple to have about 300 engineers devoted to in-house development of microLED screens.[39][40] At IFA 2018 in August, LG Display demonstrated 173" microLED display.[4]

At SID's Display Week 2019 in May, Tianma and PlayNitride demonstrated their co-developed 7.56” microLED display with over 60% transparency.[5][6] China Star Optoelectronics Technology (CSoT) demonstrated a 3.3" transparent microLED display with around 45% transparency, also co-developed with PlayNitride.[7] Plessey Semiconductors Ltd demonstrated a GaN-on-Silicon wafer to CMOS backplane wafer bonded native Blue monochrome 0.7" active-matrix microLED display with an 8-micron pixel pitch.[41][42][43]

On August 15, 2019, Luumii, a joint venture between Rohinni LLC and KoJa (Cayman) Co. Ltd., announced mass production of their micro and miniLED-based solutions for notebook computer keyboard backlights and logo lighting. Luumii's production output at their Suzhou manufacturing facility is currently 40,000 units per month and is targeting 100,000 units per month by the end of the year.[44]

At Touch Taiwan 2019 on September 4, 2019, AU Optronics demonstrated a 12.1-inch microLED display and indicated that microLED was 1-2 years from mass commercialization.[45] At IFA 2019 on September 13, 2019, TCL Corporation demonstrated their Cinema Wall featuring a 4K 132-Inch microLED dislay with max brightness of 1,500 nits and 2,500,000:1 contrast ratio produced by their subsidiary China Star Optoelectronics Technology (CSoT).[8]

References[edit]

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External links[edit]