White light emitting diodes realized by using an active packaging method with CdSe/ZnS quantum dots dispersed in photosensitive epoxy resins

Abstract

White light emitting diodes (LEDs) have been realized using the active packaging (AP) method. The starting materials were bare InGaN LED chips and CdSe/ZnS core-shell quantum dots (QDs) dispersed in photosensitive epoxy resins. Such hybrid LED devices were fabricated using QD mixtures with one ('single'), two ('dual') or four ('multi') emission wavelengths. The AP method allows for convenient adjustment of multiple parameters such as the CIE-1931 coordinate (x, y), color temperature, and color rending index (CRI). All samples show good white balance, and under a 20 mA working current the luminous efficacies of the single, dual, and multi hybrid devices were 8.1 lm W(-1), 5.1 lm W(-1), and 6.4 lm W(-1), respectively. The corresponding quantum efficiencies were 4.1%, 3.1%, and 3.1%; the CRIs were 21.46, 43.76, and 66.20; and the color temperatures were 12 000, 8190, and 7740 K. This shows that the CRI of the samples can be enhanced by broadening the QD emission band, as is exemplified by the 21.46 CRI of the single hybrid LED compared to the 66.20 value for the multi hybrid LED. In addition, we were able to increase the CRI of the single hybrid LED from 15.31 to 32.50 by increasing the working currents from 1 to 50 mA.

Efficient hybrid white light-emitting diodes by organic-inorganic materials at different CCT from 3000K to 9000K

“…In our study, the CRI of the hybrid LED device can easily achieve 85-90, which is better than traditional white LED. Moreover, compared to other studies related to quantum dot LED [24][25][26], the luminous efficiency of hybrid LED device is compatible and should be considered for the applications in the solid state lighting. Furthermore, the normalized external quantum efficacy (EQE) of the PFO polymer and blue QD with UV LED sample is shown in Fig.…”

Hybridization of CdSe/ZnS Quantum Dots on InGaN/GaN Multiple Quantum Well Light-Emitting Diodes for Pink Light Emission

“…2 shows a micrograph of pink light emission from the LED biased at 20 mA. To increase the device efficiency, QDs with higher QYs and more efficient device packagings should be adopted [11], [12].…”

Excellent Color Quality of White-Light-Emitting Diodes by Embedding Quantum Dots in Polymers Material

“…5, the luminous efficiencies of the Green B\Yellow QD\ Red QD hybrid structures with the CCTs of 5500K and 3500 K are about 11.6l m/w and 9.7l m/w, and the Green B\Yellow QD\Orange QD hybrid structures in 3500 K and 5500 K are about 17.2l m/w and 13.2l m/w, respectively. From the literature, the packaged QD w-LED can reach between 7 and 9 l m/W of luminous efficiency [44]- [46], and the major concern usually come from the low quantum yield of the QDs when they were employed in the device. On the other hand, Green B has the much higher quantum efficiency than the blue QD's and thus the overall efficacy can be greatly enhanced due to the introduction of the Green B in this experiment.…”