Study on the Separation Packaging Structure of Quantum Dot–Phosphor Hybrid White Light-Emitting Diodes for Backlight Display

The quantum dot (QD)–phosphor hybrid structure is promising for efficient white light-emitting diodes (LEDs). In this article, separation packaging structures (SPSs) having green-QD and red-phosphor configurations for backlight displays are studied. The LEDs with green-QD-down and red-phosphor-down SPSs were achieved to have the same color coordinate (0.282, 0.257) which is a typical cool white color widely used in commercial backlighting. And the optical efficiency, device cost, and thermal performances of the LEDs are comprehensively analyzed. Results indicate that the green-QD-down SPS exhibits higher backscattered loss while less conversion loss. Therefore, the green-QD-down SPS has the same optical efficiency as another structure, owing to the balance between the backscattered loss and conversion loss. The concentration differences in these two structures were discussed combining with the device cost. Moreover, the green-QD-down SPS exhibits a better heat dissipation of QDs by reducing the heat path from QDs to the lead frame, as well as less thermal power generation in conversion layers. Consequently, the maximum (39.8 °C) and minimum (31.9 °C) temperatures of its inner QD layer are 7.7% and 20.3% lower than those of the red-phosphor-down SPS at an injection current of 100 mA.