Ma Ming, Mont Frank W, Yan Xing, Cho Jaehee, Schubert E Fred, Kim Gi Bum, Sone Cheolsoo
Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, USA.
Opt Express. 2011 Sep 12;19 Suppl 5:A1135-40. doi: 10.1364/OE.19.0A1135.
We investigate the effects of the refractive index of the encapsulant on the light-extraction efficiency (LEE) of light-emitting diodes (LEDs) for GaN LEDs (n ≈ 2.5) and AlGaInP LEDs (n ≈ 3.0). For non-absorbing rectangular parallelepiped LED chips, as the refractive index of the encapsulant increases, the LEE first increases quasi-linearly, then increases sub-linearly, and finally a saturation is reached. Furthermore, LEDs with a dual-layer graded-refractive-index (GRIN) encapsulant (n(encapsulant 1) = 1.57 and n(encapsulant 2) = 1.41) is fabricated through a two-step curing process. We demonstrate that such an LED further enhances the LEE by reducing Fresnel reflection loss at the encapsulant/air interface by 35% compared with an LED encapsulated with a single-layer encapsulant (n(encapsulant) = 1.57).
我们研究了封装材料的折射率对氮化镓发光二极管（GaN LED，n≈2.5）和铝镓铟磷发光二极管（AlGaInP LED，n≈3.0）的发光二极管（LED）光提取效率（LEE）的影响。对于非吸收性长方体LED芯片，随着封装材料折射率的增加，LEE首先近似线性增加，然后亚线性增加，最终达到饱和。此外，通过两步固化工艺制造了具有双层渐变折射率（GRIN）封装材料（n（封装材料1）=1.57且n（封装材料2）=1.41）的LED。我们证明，与采用单层封装材料（n（封装材料）=1.57）封装的LED相比，这种LED通过将封装材料/空气界面处的菲涅尔反射损耗降低35%，进一步提高了LEE。
