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We have demonstrated the fabrication and characterization of hybrid CdSe-ZnS quantum dot (QD)-InGaN-GaN quantum well (QW) red light-emitting diodes (LED). The red-emitting QD-resin blend was dropped on the InGaN blue LED to complete the device fabrication. With proper blend ratio, the blue light from the InGaN QWs can be effectively down converted to the red light. In our case, when the QD concentration is as high as 40 mg/1 ml of resin, the luminous flux from the hybrid LED biased at 20 mA is 0.65 lm, from which the luminous efficiency of 9.3 lm/W can be obtained. Also, the corresponding electroluminescence spectrum exhibits the contribution of red light emission to the total light intensity is 98%, while the Commission Internationale de l'Eclairage chromaticity coordinates of the red light are (0.635, 0.275). However, the coordinates would be gradually shifted with current increasing from 10 to 60 mA due to the fluctuation of red/blue light ratio and thermal effect.
Date of Publication: July 2008