Improvement of light extraction efficiency of InGaN light emitting diodes (LEDs) using polydimethylsiloxane (PDMS) concave microstructures arrays was demonstrated. The size effect of the concave microstructures on the light extraction efficiency of III-Nitride LEDs was studied. Depending on the size of the concave microsturctures, ray tracing simulations show that the use of PDMS concave microstructures arrays can lead to increase in light extraction efficiency of InGaN LEDs by 1.4 to 1.9 times. Experiments utilizing 1.0 μm PDMS concave microstructures arrays demonstrated 1.60 times improvement in light extraction, which is consistent with simulated improvement of 1.63 times. The enhancement in light extraction efficiency is attributed to increase in effective photon escape cone due to PDMS concave microstructures arrays, and reduced Fresnel reflection within the photon escape cone due to the grading of refractive index change between GaN / PDMS / air interface.

Date Published: 3 February 2009
PDF: 7 pages
Proc. SPIE 7231, Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XIII, 72310U (3 February 2009); doi: 10.1117/12.808600

Published in SPIE Proceedings Vol. 7231:
Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XIII
Klaus P. Streubel; Heonsu Jeon; Li-Wei Tu, Editor(s)