60 Market focus: LEDs Hopes for mini-/micro-LED …

1 The world is awash withliquid-crystal displays(LCDs) from tiny indicator panels, throughmobile phones, up to giant television screens. Most LCDs,particularly those with colorcapabilities, incorporate a backlight that now consists oflight-emitting diodes (LEDs). In operation, the LCD part ofthe screen blocks or transmitslight to give an image. While LEDs have reducedpower consumption comparedwith the previous system based on fluorescent tech-nology, much of the light that is produced is wasted a black screen consumes as much power as white.

2 This is a problem both for the giant TVs and for mobiledevices, where energy consumption reduces batterycharge. Developers of micro-LEDs plan to give every pixel an independent light-emitting source, cutting the backlight waste the power consumption of futuremicro-LED displays is estimated at 10% that of , this principle is used in large outdoor displayswith arrays of regular-size LED devices, but close-rangedisplays TVs, smartphones, etc need LEDs are of the order (500 m).Reducing the size to about a fifth gives 100 m mini-LEDs,which find application in ultra-fine pixel-pitch displaysfor control rooms and indoor panels use arrays of individual red-green-blue(RGB) devices of less than 30 m, and even down m.

3 Panels with micro-LEDs should be able to meetresolutions of 2000 6000 pixels-per-inch (ppi), muchhigher than the 400ppi used in retina LCD from cutting the backlight waste, LED-baseddisplays are competing with organic LEDs (OLEDs),which have been in development for a couple ofdecades. The promise of inorganic LEDs is reduced power con-sumption along with higher brightness and contrast,even compared with OLEDs. Power consumption ofmicro-LED displays is expected to be 50% that ofOLEDs. Micro-LED development is aimed at improvingthe quality and uniformity of epitaxial wafers neededfor high yield and low cost.

4 Further hoped-for advantages include ultra-high resolution, high color saturation, quick response andlong lifespan (Table 1).The adoption of micro-LED technology depends oncosts being closer to LCD panels than OLED panels $12 15 for a LCD compared with $65 70 foran active-matrix OLED display as used in the iPhone costs for micro-LED panels are projected tobe reduced significantly by 2021. Meanwhile, Japan sYano Research Institute expects the global micro-LEDmarket to increase from $7m this year to $224m in2020.

5 In addition to offering a performance target, OLED salso stand as a warning to crystal-ball gazers. Many inthe industry, including Samsung (2006), expected thetechnology to replace LCDs as the mainstream displaytechnology. OLEDs were expected to deliver low powerconsumption, simple structure, wide color gamut,large viewing angles under sunlight, and quickresponse time, in a compact format. OLED panels do consume less power, but they havealso not realized early expectations in this regard, withsavings falling below the original Hopes by about 30%.

6 Another problem is that manufacturing processesusing organic materials have low yields for the highestperformance, increasing costs. Market focus: LEDs semiconductorTODAYC ompounds&AdvancedSilicon Vol. 12 Issue 9 November and Market analysts suggest that mass production could start inthree to five years, or even sooner in niche applications, reports Mike for mini-/micro-LEDdisplay Market space invasionDisplay technologyLCDOLEDM icro-LEDM echanismBacklight/LEDSelf-emissiveSelf-e missiveContrast ratio5000.

7 1 LifespanMediumMediumLongResponse timems snsOperating temperature 40 C to 100 C 30 C to 85 C 100 C to 120 CPower consumptionHighMediumLowView angleLowMediumHighPixel per inchup to 800ppi500ppi>2000ppiCostLowMediumHighTab le 1. LEDI nside s view of advantages and disadvantages of differentdisplay many ways, it is not the LED technology that needsimprovement rather production costs and integrationinto the display production supply chain stand as thepresent challenges. The micro-LEDs must be accuratelytransferred and fixed en masse in a way that competeswith LCD process speeds (with 10G panels produced inseconds).

8 Such manufacturing needs to separate epitaxial layersof micron-sized RGB LEDs from their substrates andtransfer them onto a receiver substrate that could beglass or some flexible polymer. At the same time, theLEDs need to be connected with the control circuits onthe receiver substrate. Different companies see a variety of routes to massmicro-LED panel adoption, while costs are being markets employing advanced capabilities couldcome first for micro-LED panels. For example, LCDs and OLEDs both perform relativelypoorly in competition with bright sunlight.

9 Outdooractivity smart wearable devices could thus benefit fromsmall but high-brightness screens. Ditto automotive windshield displays, with 80%transparency for micro-LED panels, compared with40% for OLEDs. Small indoor screens for virtual/augmented reality(VR/AR) have 20% wider color gamut than OLEDs;and, at the other end, large-scale indoor displays,which could benefit from the variable shapes and areasof flexible panels, are also variously proposed. Already, end-user companies such as Apple and Sonyare developing micro-LED-based products.

10 Sony sCrystal LED Integrated Structure (CLEDIS) giant displaysuses ultrafine RGB LED areasmounted on a black display surface (Figure 1). At the other end of the supply chain, Epistar s presidentJou Ming-jiunn commented in a June Digitimes reportthat US-based companies are inclined to apply micro-LED technology to wearables, VR and AR devicesinitially and then smartphones, while Asia-based firms,such as Samsung Electronics, are targeting large-sizedevices such as TVs. Epistar plans to produce 6-inchmicro-LED epitaxial wafers, and possibly micro-LEDchips, using existing equipment (which presently produces 4-inch LED epitaxial wafers) to meet thesedemands.