Wang Hao, Lee Kyu-Seung, Ryu Jae-Hyoung, Hong Chang-Hee, Cho Yong-Hoon
National Research Laboratory for Nano-Bio-Photonics, BK21 Physics Program and Department of Physics, Chungbuk National University, Cheongju 361-763, Korea.
Nanotechnology. 2008 Apr 9;19(14):145202. doi: 10.1088/0957-4484/19/14/145202. Epub 2008 Mar 4.
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.
通过有源封装（AP）方法实现了白色发光二极管（LED）。起始材料是裸露的氮化铟镓LED芯片以及分散在光敏环氧树脂中的硒化镉/硫化锌核壳量子点（QD）。使用具有一种（“单波长”）、两种（“双波长”）或四种（“多波长”）发射波长的量子点混合物制造了这种混合LED器件。AP方法允许方便地调整多个参数，如CIE-1931坐标（x，y）、色温以及显色指数（CRI）。所有样品均显示出良好的白平衡，并且在20 mA工作电流下，单波长、双波长和多波长混合器件的发光效率分别为8.1 lm W⁻¹、5.1 lm W⁻¹和6.4 lm W⁻¹。相应的量子效率分别为4.1%、3.1%和3.1%；显色指数分别为21.46、43.76和66.20；色温分别为12000、8190和7740 K。这表明通过拓宽量子点发射带可以提高样品的显色指数，例如单波长混合LED的显色指数为21.46，而多波长混合LED的值为66.20。此外，通过将工作电流从1 mA增加到50 mA，我们能够将单波长混合LED的显色指数从15.31提高到32.50。
