Displays based on inorganic light-emitting diodes (LED) are considered as the most promising one among the display technologies for the next-generation. The chip for LED display bears similar features to those currently in use for general lighting, but it size is shrunk to below 200 microns. Thus, the advantages of high efficiency and long life span of conventional LED chips are inherited by miniaturized ones. As the size gets smaller, the resolution enhances, but at the expense of elevating the complexity of fabrication. In this review, we introduce two sorts of inorganic LED displays, namely relatively large and small varieties. The mini-LEDs with chip sizes ranging from 100 to 200 μm have already been commercialized for backlight sources in consumer electronics applications. The realized local diming can greatly improve the contrast ratio at relatively low energy consumptions. The micro-LEDs with chip size less than 100 μm, still remain in the laboratory. The full-color solution, one of the key technologies along with its three main components, red, green, and blue chips, as well color conversion, and optical lens synthesis, are introduced in detail. Moreover, this review provides an account for contemporary technologies as well as a clear view of inorganic and miniaturized LED displays for the display community.

We investigate divergent behaviors in the emission of blue and green light-emitting diodes (LEDs) when they are subjected to the current-stress aging. Microscopic hyperspectral imaging is introduced to measure spatially resolved mappings of the peak intensity, the peak energy, and the full width at half maximum. Also, plots of external quantum efficiency versus injection current are measured to determine the extent of the Shockley-Read-Hall (SRH) nonradiative recombination rate based on the two-level model. As a result, a phenomenological model is proposed to account for the competitive mechanism between the carrier localization and the SRH recombination. In the blue LED case, the increase in the radiative recombination within localization states cancels the SRH nonradiative recombination within point defects. While in the green LED case, the enhancement of SRH recombination and the remission of carrier localization jointly kill the radiative recombination.

A solution for multi-functional indoor light sources is proposed to achieve the new concept of healthy lighting. A remotely controllable light source that embodies a quadruple-chip light-emitting diode and driven by pulse-width-modulation currents is designed. Therefore, spectral power distributions (SPDs) of the light source can be readily controlled. An algorithm, namely the optical power ratio algorithm, is developed to select all suitable SPDs adapted for various applications. Principles of selection are based on those traditional visual indices, as well as on some non-visual parameters such as circadian action factor, circadian efficacy of radiation and circadian illuminance. We investigate in detail the correlation among these parameters and provide SPDs with both decent visual and non-visual performances for three typical cases. The study suggests some fundamental principles for designing healthy light sources, and can be regarded as a guide for designing indoor light sources of the next generation.

The distributions of the electroluminescence of AlGaInP-based flip-chip red light-emitting diodes with a size of $100\,\,\mu \text{m}\,\,\times 200\,\,\mu \text{m}$ have been obtained via microscopic hyperspectral imaging by capturing spatially resolved light emission from the side of a transparent substrate. As the injected DC current exceeds the current corresponding to the maximum external quantum efficiency, the light emission from the current crowding region decreases due to the self-heating effect, whereas the emission of the region corresponding to the anode becomes dominant due to the low heat resistance.