研究目的
Investigating the lifetime and reliability of Phosphor-Quantum dot (QDs) based white LEDs under various stress conditions including blue light luminance, temperature, and moisture.
研究成果
Light is a dominant factor causing rapid lumen degradation in QD-LEDs, especially when combined with temperature and moisture. Temperature alone does not significantly affect degradation until moisture penetrates the package. The study uncovers new degradation mechanisms, suggesting the need for improved reliability for outdoor applications.
研究不足
The study identifies new degradation mechanisms but notes that their detailed investigation is yet to be conducted. The impact of temperature alone on QD-phosphor based LED lumen degradation is hypothesized but not verified, indicating a need for future work.
1：Experimental Design and Method Selection:
The study involves preparing packaged white LEDs with blue LED as a light source and down conversion materials (green phosphor and red QDs). Silicone is used as an encapsulant. LEDs are divided into sets and tested under varying conditions to observe lumen degradation.
2：Sample Selection and Data Sources:
15 packaged white LEDs are prepared and divided into 3 sets of 5 LEDs each, tested under different conditions.
3：List of Experimental Equipment and Materials:
Keithley power source 2502 for powering LEDs, TeraLED integrating sphere from Mentor Inc. for measuring optical characteristics, and environmental test chamber KD-162-FUL from KING DESIGN for high temperature and moisture tests.
4：Experimental Procedures and Operational Workflow:
LEDs are tested under ambient conditions with LED ON, 85oC/85%RH with LED OFF, and 85oC/85%RH with LED ON. Luminous fluxes are measured at different durations.
5：Data Analysis Methods:
The variation of percentage luminous flux degradation is analyzed to observe the effect of stress factors on LED performance.
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