Zhu Peifen, Tan Chee-Keong, Sun Wei, Tansu Nelson
Appl Opt. 2015 Dec 1;54(34):10299-303. doi: 10.1364/AO.54.010299.
Light extraction efficiency of thin-film flip-chip InGaN-based light-emitting diodes (LEDs) with a TiO2 microlens arrays was calculated by employing the finite-difference time-domain method. The microlens arrays, formed by embedding hexagonal close-packed TiO2 sphere arrays in a polystyrene (PS) layer, were placed on top of the InGaN LED to serve as an intermediate medium for light extraction. By tuning the thickness of the PS layer, in-coupling and out-coupling efficiencies were optimized to achieve maximum light extraction efficiency. A thicker PS layer resulted in higher in-coupling efficiency, while a thinner PS layer led to higher out-coupling efficiency. Thus, the maximum light extraction efficiency becomes a trade-off between in-coupling and out-coupling efficiency. In addition, the cavity formed by the PS layer also affects light extraction from the LED. Our study reveals that a maximum light extraction efficiency of 86% was achievable by tuning PS thickness to 75 nm with maximized in-coupling and out-coupling efficiency accompanied by the optimized resonant cavity condition.
采用时域有限差分法计算了具有TiO₂微透镜阵列的薄膜倒装芯片氮化铟镓基发光二极管（LED）的光提取效率。通过将六方密堆积的TiO₂球体阵列嵌入聚苯乙烯（PS）层中形成微透镜阵列，并将其放置在氮化铟镓LED顶部，作为光提取的中间介质。通过调整PS层的厚度，优化了内耦合和外耦合效率，以实现最大光提取效率。较厚的PS层导致较高的内耦合效率，而较薄的PS层则导致较高的外耦合效率。因此，最大光提取效率成为内耦合和外耦合效率之间的权衡。此外，PS层形成的腔也会影响LED的光提取。我们的研究表明，通过将PS厚度调整到75nm，在最大化内耦合和外耦合效率并伴随优化的谐振腔条件下，可实现86%的最大光提取效率。
