Design of approximately omnidirectional broadband anti-reflection coating
Date Issued
2008
Date
2008
Author(s)
Yeh, Chih-Yong
Abstract
In this thesis, we applied the multilayer theory and conjugate gradient optimization method to design the anti-reflection coating layers for GaN-based light emitting diode (LED) and crystalline silicon solar cells. Based on the refractive indices (2.03 and 1.46) of SiOxNy thin films fabricated by RF reactive magnetron sputtering, we designed approximate broadband omnidirectional anti-reflection coating using numerical computation. A merit function was defined to estimate the performance of anti-reflection coating for wide incident angle within the visible range, Using the two-layer anti-reflection design with layer refractive indices of 2.03 and 1.46, our optimized reflectance of bi-layer antireflection coating is about 4.46%, which is averaged over wavelength range of 400 ~ 700nm and incident angle range of 0˚~70˚ . For LEDs, average reflectance (below critical angle ~ 24˚) as low as 3.04% and 3.05% are achieved for blue light (wavelength centered at 470nm) and green light (wavelength centered at 525nm), respectively. In this study, we also found that more accurate control of the bilayer thickness is required while taking broad wavelength and wide incident angle into account.
Subjects
anti-reflection coating
conjugate gradient method
wide angle
Type
thesis
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