Optimal ways of colour mixing for high‐quality white‐light LED sources

Abstract

In this paper, the first time reported the full color active matrix micro-LEDs (AMLEDs) display with high transparent over 40% which is based on top gate IGZO TFT (Thin film transistor) backplane. This AMLEDs display was successfully developed with flip chip RGB micro-LEDs that can achieve more than 108% NTSC gamut, while the display is also brighter than 400nits.

Multi‐color monolithic III‐nitride light‐emitting diodes: Factors controlling emission spectra and efficiency

“…Its disadvantages include the necessity of separated current control of various LEDs, temperature mismatch of their operation conditions , and different degradation rates of the LEDs made from nitride and phosphide compounds. In addition, because of the well‐known “green‐gap” problem, i.e., considerable efficiency reduction of both nitride and phosphide LEDs in the spectral range of 500–600 nm, the overall efficacy of such a type of light source is still behind that typical for conventional phosphor‐converted LEDs . In this situation, continuous attention of researches is attracted to multi‐color III‐nitride LEDs, as their combination with a suitable phosphor or a phosphor mixture may provide acceptable compromise between the demanded efficacy and other white light characteristics.…”

Superior color rendering with a phosphor‐converted blue‐cyan monolithic light‐emitting diode

“…Assuming a Gaussian shape of both LED emission lines with the same width and using incomplete optimization of the color mixing (the magnitude ratio of two emission lines was fixed), improvement in CRI from 78 (CCT = 4000 K at λ p = 475 nm) for the reference blue pc-LED to 91 (CCT = 5800 K at λ 1 = 435 nm and λ 2 = 490 nm) has been predicted. Our simulations with the realistic asymmetric emission spectra and wavelength-dependent widths [13] provide rather different results presented in Figure 2. Firstly, a singlewavelength pc-LED (λ p < 460 nm and YAG:Ce 3+ phosphor) is predicted to provide a higher CRI (up to 80) at CCT < 6000 K than dual-wavelength PC-LEDs.…”

Insight into the impact of atomic- and nano-scale indium distributions on the optical properties of InGaN/GaN quantum well structures grown on m-plane freestanding GaN substrates

“…Cross-sectional TEM samples and APT samples were prepared using a dual-beam focused ion beam microscope (FIB: FEI Helios NanoLab TM ) through an in-situ lift-out approach, in which a final clean-up procedure involving combined low FIB voltages and currents was used to minimize beam-induced damage to the samples 28 . The TEM lamellae were prepared with an approximately a-direction [11][12][13][14][15][16][17][18][19][20] surface normal, and the APT sample was mounted on a standard silicon (Si) coupon with an array of pre-shaped flat-topped Si posts. A TEM microscope (FEI Titan 3 80-300 kV) with a probe corrector was used for high resolution STEM (scanning TEM) imaging at 300 kV, where the image was acquired whilst the electron beam was parallel to the a-zone axis [11][12][13][14][15][16][17][18][19][20] of the sample.…”

“…In the presence of competing non-radiative recombination pathways, this can be a contributory factor to the degradation of the internal quantum efficiency of the emission 16,17 . This issue is particularly pressing in green and amber emitting LEDs, which exhibit much lower efficiencies than their blue counterparts and is referred to as the 'green gap' problem 1,2,18,19 . Whilst the precise cause of the green gap is controversial, the decreased electron-hole wavefunction overlap in QWs at higher indium contents is frequently cited as a contributory factor 2 .…”

“…InGaN QWs grown on non-polar crystal orientations (such as m-plane (1-100) and a-plane (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)) are ideally free of macroscopic built-in electrostatic fields; this provides a potential route to fabricate green emitting devices with improved optical performance because of the increased electron-hole wavefunction overlap. This is the motivation behind our efforts to study the structural and optical properties of non-polar QWs with varying indium contents, and to specifically investigate the role of the indium distribution in controlling the optical properties of QW systems emitting at longer wavelengths.…”