Phosphor Free High-Luminous-Efficiency White Light-Emitting Diodes Composed of InGaN Multi-Quantum Well

Using Three-Component Hierarchical Structures to Improve the Light Extraction From White Leds Based on Red-Green-Blue Color Mixing Method

“…And because of the non-radiative recombination of the phosphors, the efficiency the white LEDs based on phosphor conversion cannot reach 200 lm/W. On the other hand, since the RGB system white LEDs are phosphors free, the lifetime and color rendering are much better than the phosphor conversion white LEDs, and it is expected that their emission efficiency can reach 250 lm/W, so the white LEDs based on color mixing are becoming the main trend of white LEDs [6,7].…”

Design analysis of phosphor-free monolithic white light-emitting-diodes with InGaN/ InGaN multiple quantum wells on ternary InGaN substrates

“…4(b), it shows that both LEDs (A) and (B) on ternary substrate have the peak EQE (∼ 50%) with J ∼ 10 -15 A/cm 2 , which is significantly higher than that of InGaN/ GaN monolithic white LED on conventional GaN substrate (EQE ∼ 20%). 7 Despite the fact that LED (C) shows a higher EQE peak (∼ 68%) at J ∼ 25 A/cm 2 , it has a much severe droop towards higher current densities, which is attributed from poorer carrier confinement without any of the GaN thin barrier design. More importantly, only green color illumination can be obtained from LED (C) while white color illumination can be achieved by LEDs (A) and (B) with comparable output power and EQE.…”

“…[6][7][8][9][10][11][12][13][14][15][16][17][18][19] Previous works have reported the possibility of fabricating phosphor-free monolithic white LED by stacking multi-color-emitting InGaN/ GaN quantum wells (QWs) on GaN substrate. [6][7][8][9][10] However, it is very challenging to incorporate high In-content into InGaN/ GaN QWs on GaN substrate which is critical for green and yellow emission wavelengths due to charge separation issue from large lattice-mismatch strain. 20,21 On the other hand, nanostructure engineering approaches such as the use of quantum dots, 11,12 nanowires, 13 substrates 18,19 have also been pursued previously to achieve white LEDs.…”

“…Nanostructure engineering has been conducted to the multiple QWs (MQWs) active region on ternary substrate to achieve white color illumination. Simulation studies show that the proposed and optimized white LED device structure exhibits ∼2 times larger external quantum efficiency (EQE) 7 and higher light output power as compare to conventional InGaN/ GaN white LEDs on GaN substrates. [6][7][8][9][10] The chromaticity coordinates and correlated color temperature (CCT) of the proposed white LEDs on ternary substrates also demonstrated comparable results with those nanostructured white LEDs.…”

“…Simulation studies show that the proposed and optimized white LED device structure exhibits ∼2 times larger external quantum efficiency (EQE) 7 and higher light output power as compare to conventional InGaN/ GaN white LEDs on GaN substrates. [6][7][8][9][10] The chromaticity coordinates and correlated color temperature (CCT) of the proposed white LEDs on ternary substrates also demonstrated comparable results with those nanostructured white LEDs. 14,15 Note that the strain in InGaN/ InGaN QW on ternary InGaN substrate can be reduced by up to ∼75% compared to conventional InGaN/ GaN QW on GaN substrate as pointed out by previous work.…”