The real-world application of microLEDs and microICs in displays and related devices requires that the products be robust to demanding environmental stresses. This study investigates the reliability of a microLED display that was designed and built to serve as the pixelated light source within a liquid-crystal-on-Silicon (LCOS) projection display for augmented reality (AR) systems. Two types of reliability tests, high temperature operating life (HTOL) and temperature cycling (TC) were conducted on six microLED displays from three different fabrication campaigns. The yield, brightness, and electrical currents were measured to characterize the performance of the display pixels before and after reliability tests. All the display samples passed HTOL and TC tests with slight current changes and varying levels of brightness variation. This study provides novel and encouraging results regarding the reliability of transfer-printed microscale LEDs and ICs, and the novel interconnection methods used to assemble the displays.

MicroIC enables display attributes unattainable from polycrystalline thin‐film transistors, and the complimentary metal‐oxide semiconductor (CMOS) microICs support a wide range of applications beyond driving pixels. Integrating sensors within displays can add value to products, reduce costs and improve performance versus conventional solutions. As evidenced by touch and display integration in mobile displays via TDDI ICs, in‐cell sensing can reduce cost and improve performance to levels that are not available with all display types. Capacitive touch, optical touch, 3D scanning, and proximity sensing can also benefit from the inherent coordination between sensors and display. We present multiple sensing architectures and demonstrations of integration within microLED displays and describe CMOS microIC circuits for touch sensing applications. With diverse heterogenous semiconductor technology tightly woven into displays, the potential for intuitive gesture controls, adaptive interfaces, and enhanced sensory feedback paves the way for more natural and effortless interactions between humans and machines.

Advances in the brightness, efficiency, and dynamic range of emissive displays are made possible by integrating microLEDs inside every pixel. Economical realization of these displays demands a diverse set of process technologies and device designs to accommodate the characteristics of microLEDs in large‐area formats. Here, we present advancements in stamp‐based mass transfer. We present schemes for packaging microLEDs into multi‐color emitter structures that interface readily with backplane materials. The structures reduce mass transfer cost by increasing parallelism of the process. We demonstrate their utility in active pixel arrays that use microICs as drivers. We introduce a coverglass with light trap film stacks for enhancing contrast in microLED displays. Finally, we present a surface mountable device that incorporates these technologies into a format that is applicable to videowalls and digital signage.

Displays that utilize millions of tiny microLEDs promise a future generation of phones, computers and televisions that are bright enough for sunlit environments yet consume less power. The microLEDs are made using wafer-level semiconductor processes, and key to manufacturing displays is the capability to assemble billions of microLEDs onto panels. Elastomer stamp transfer printing is a mass transfer technology with the yield, accuracy, speed, and scalability required to meet the demands of display manufacturing. The versatility of elastomer stamp transfer leads to further innovations for displays, these include the ability to integrate miniature integrated circuits, called microICs, for advanced backplanes and strategies where microLEDs are combined into PixelEngine packages on intermediate substrates before final assembly to the display panel. This paper reviews how transfer printing has been applied to microLED display development to date and describes a pixel-driver microIC with vertically integrated microLEDs, called PixelEngineAll-in-One, that performs all pixel functions and is designed to enable displays realized through assembly onto passive wiring panels.

Industry‐wide efforts to develop microLED technology for displays brought focused attention to the importance of mass transfer micro‐assembly. Processes that are compatible with high‐volume manufacturing that can rapidly manipulate millions of discrete micron‐scale semiconductor objects per product unit are a new technological capability and required for making microLED displays accessible to mainstream consumer applications. As those assembly processes become mature, new attention shifts to the microLED devices themselves and to electronic driving schemes to operate them. Furthermore, mature mass transfer processes make possible new semiconductor constituents to the backplane, including singlecrystal devices with levels of integration density that are not natively available to display panel manufacturing. This confluence of new requirements and new possibilities sets a stage for far‐reaching innovation in consumer displays. This paper describes designs for microLED displays that use micron‐scale full color emitter packages and micron‐scale driver elements (microICs) that control clusters of pixels. A combination of mass transfer and conventional backplane fabrication processes is suitable for making displays of these designs, and the resulting products will support more than 300‐400 pixels per inch with advantageous power consumption characteristics.

Micro-transfer-printing (µTP) enables the intimate integration of diverse non-inherent functionalities on a target substrate and hence allows for the realization of complex photonic integrated circuits (PICs) with small footprint. By employing a polydimethylsiloxane (PDMS) elastomeric stamp with an array of posts, a large number of micro-components can be integrated on a target wafer in one transfer printing operation, which leads to substantial cost reduction of the resulting PICs. This paper discusses the use of µTP for the realization of III-V lasers on Si and SiN PICs and summarizes the recent progress that has been made in this field.

Emissive displays using microLEDs will be bright, rugged, and efficient. Realization of microLED displays requires high‐yield mass transfer processes that rapidly assemble millions of micron‐scale devices onto non‐native display substrates. A candidate mass transfer process uses polydimethylsiloxane (PDMS) elastomer stamps to retrieve and transfer large arrays of microLEDs. This paper will review the fundamentals of elastomer stamp mass transfer and will examine paths to satisfy the demanding throughput requirements for display manufacturing.

Flat panel displays are ubiquitous and dominated today by liquid crystal and OLED technologies. Increasingly, there is an expectation that microLED will exhibit superior performance metrics and become a new mainstream category of flat panel displays. They have the potential to be very bright, to be power efficient, and to enable new within-panel capabilities. High-throughput, high-yield, mass transfer technologies that accurately and cost-effectively integrate large arrays of wafer-fabricated microdevices onto non-native display substrates are key enablers for microLED displays. Transfer-printing with elastomer stamps is a candidate mass transfer technology for making next generation displays. A variety of microLED displays, including displays controlled with transfer-printed microICs, have been designed and fabricated using elastomer stamp transfer-printing.

The incumbent flat-panel technologies, liquid crystal display (LCD) and organic light-emitting diode display (OLED), are ill-suited to produce compact, efficient, and robust high-brightness displays. LCDs are very inefficient, only a small fraction (~5%) of the generated light exits the display. To achieve highbrightness LCDs, practitioners create extremely bright back-light units using inorganic LEDs which require expensive and unreliable active cooling solutions. OLEDs use organic molecules to form light emitting diodes within each display pixel. The lifetime of the organic light emitters is inversely proportional with the display brightness; therefore, OLEDs are not suitable for highbrightness applications. In sharp contrast, inorganic LEDs made using wafer-level semiconductor technology are long-lived, even when operating at high luminance. Displays that use inorganic LEDs as the light-emitters within each display pixel already dominate the giant video walls that increasingly decorate our highways and streetscapes. Today, there are many efforts around the world aimed at making highly miniaturized inorganic LEDs, called microLEDs, and developing methods to transfer those microLEDs from their native substrate to the destination display substrate. Effective techniques to produce microLED displays must have the capability to quickly and accurately transfer millions of microscale devices and are called "mass transfer" technologies. Micro-transfer-printing using elastomer stamps is one such "mass transfer" technology that has been used to produce prototype microLED displays. Here, we will describe how micro-transfer-printing combined with wafer-level packaging techniques can produce highbrightness displays. We will provide fabrication details and characterization results of various 5.1" 70 PPI microLED displays. In one example, we produced a monochrome green display using 8 μm x 15 μm flip-chip InGaN microLEDs with a maximum brightness in excess of 30,000 nits. We will highlight application opportunities and remaining challenges for high-brightness displays using microLEDs.

Micro transfer printing (μTP) is a useful method for heterogenous integration of micro-scale devices but typically requires additional electrical interconnection of devices following print. In this paper, the concept of interconnect at print is explored and a stacked configuration demonstrating electrical interconnection of 3-D micrometer scale electrical devices is shown. Structures that are 45μm by 25μm consisting of four metallized spikes on the bottom and recessed pyramids at the top are stacked, probed, and shown to illuminate light demonstrating their electrical interconnection from print.

MicroLED flat panel displays offer performance advantages that cannot be matched by OLED or LCD, and there is a growing industry consensus that microLED will become the next major flat panel display category. At present, leading companies are demonstrating steady progress against the technological challenges that historically impeded the commercialization of microLED displays, such as those related to mass transfer in manufacturing and efficient fabrication of low‐current, micron‐scale optoelectronic devices. Equally important and also challenging is the pixel‐level circuitry that can efficiently and reliably drive the emitters in these displays. Mass transfer for microLED displays most frequently refers to the process used to distribute small LEDs across a display substrate, but it can also open entirely new advantageous possibilities in backplane design. Mass transfer of microIC drivers as pixel engines for microLED displays is gradually receiving increased attention as a path toward unmatched efficiency, dynamic range, and brightness. This pixel engine display manufacturing approach provides key enabling factors for capital‐efficient, near‐term implementation of microLED displays for consumer markets.

Micro-transfer-printing (µTP) enables the intimate integration of a variety of III-V opto-electronic components on silicon photonic integrated circuits (Si PICs). It allows for the scalable manufacturing of complex III-V/Si PICs at low cost.

Micro-transfer-printing enables the intimate integration of a wide range of opto-electronic micro-components on a silicon photonics platform. This technique allows for wafer-scale integration in a massively parallel manner with high alignment accuracy, high throughput and high yield, therefore leading to a cost reduction of complex photonic integrated circuits.

Micro-transfer-printing is a key enabling technology for the heterogeneous integration of different materials and devices. The technique is particularly applicable to photonics where a typical system requires diverse arrays of components.

III-V opto-electronic devices (photodiodes, etched facet lasers) are micro-transfer-printed onto silicon waveguide circuits. An alignment-tolerant interface for evanescently-coupled devices is proposed enabling III-V/Si heterogeneously integrated PICs using micro-transfer-printing.

Transfer-printing provides a highly versatile methodology to heterogeneously and intimately integrate diverse photonic and electronic components in close proximity onto silicon photonics platforms.This technique can enable a manufacturing route to powerful photonic integrated circuits.

Photovoltaic modules hub type (CPV) comprises a base plate having thereon a solar cell array 1 mm2 or smaller. There is also provided an interconnecting network backplane on the motherboard. This interconnection network backplane operates to electrically connect the solar cell array. There is also a front plate, which is separate from the motherboard. This front plate includes a main matrix thereon which face the solar cell array lenses. The front plate is configured to provide the solar cell array lens-to-cell concentration of more than 1000X. To achieve this concentration of lens-to-cell 1000X light, the main lens can be configured as plano-convex lenses with a lens curvature of less than 4 mm. It can also provide a matrix of secondary optical element, which extends between the main lens array and the solar cell array.