Optical Spectrum And Package Structure Optimization Of QCLED

Quantum dots converted light emitting diode(QCLED) is a new-style lighting device with quantum dots(QDs) as the down conversion material. The color rendering index(CRI) of QCLED is higher than conventional LED, but the luminous efficiency(LE) and thermal stability are somewhat inferior. Therefore, the task of our study is to develop the strengths, and to avoid the weaknesses of QCLED: we developed the CRI and LE through spectrum optimization, and promotes the thermal stability and LE through package structure optimization.The optical spectrum of QCLED is the primary factor of CRI and one of the determinant of LE. Unfortunately, former researches about the spectrum optimization of QCLED mainly employed experimental attempt without theoretical guidance, which was rather blindfold. Therefore, firstly, we conducted a genetic algorithm to optimize the spectrum with the target of high CRI and LE at correlated color temperature(CCT) of 3000K~6000K. Secondly, taking the optimal spectral as guidance, we packaged the QCLEDs with 3 kinds of quantum dots, and finally obtained the QCLEDs with Ra>91,LER>260 lm/Wopt at CCT=3000K~6000K.Meanwhile, the package structure of QCLED is one of the important determinant of LE and thermal stability. On one hand, package structure will influence the optical energy loss on the path of light propagation and then affect the LE of QCLED. So we conducted an experiment to compare the LE of three kinds of QCLEDs, which were packaged with air gap, silicone lens and silicone filler, respectively. It turned out that, the LE of QCLED with silicone filler showed 52% and 31% higher than that with air gap and silicone lens, respectively. On the other hand, the package structure will influence the heat generation and dissemination in the QCLED, afterwards, affect the temperature of QDs film and then the thermal stability. So we measured the energy generation of the QCLEDs and conducted simulations and experiments to compare their thermal characteristics. Under the drive current of 300 mA, the top temperature of QCLED with silicone filler is 24.1? and 24.4?lower than the other two, respectively. Meanwhile, with the drive current raising from 50 mA to 500 mA, the decrease amplitude of silicone filler was only 16.8% and 30.4% of the other two structures, respectively. Therefore, the QCLED with silicone filler revealed the optimal performance on LE and thermal stability.