Effect of Surface Texturing on The Angular Dependent Optical Behaviors of Solar Cells and Vertical-Injection Light-emitting Diodes
Date Issued
2012
Date
2012
Author(s)
Wang, Yu-Ting
Abstract
Various applications of nanoparticles, such like nanosphere lithography, is believed to be a fast and simple way to fabricate surface nanostructures and thus improve the performance of photonic device such as solar cell or LED. However, there’re still some issues and mechanisms behind not investigated or explained thoroughly, such like the polarization-dependent reflectivity of the incident light for solar cells or the texture-related radiation behaviors of the extracted guided light.
With the focus on the first issue, for solar cells, investigations had been made by comparing the properties of cells with silica nanospheres coated to the one without any surface structure. We found that the silica nanosphere arrays can improve the TE polarized light more significant than TM polarized light, which is a good way to compensate the larger reflectivity in TE polarized light for oblique incidence.
In the second part, for vertical-injection LED (VLED), besides one-step nanorod surface patterning, a two-step surface patterning with the addition of truncated microdome arrays is further employed and investigated. The results suggest that light will be radiated to various angles while interacting with different single-step textured surfaces. As for the hybrid structure, since separate guided modes in the semiconductor layers are diffracted by either nanorods or microdomes, the percentage increase of light extraction from it is found to be about the linear superposition of both types of single surface textures at certain corresponding angle domain. The result provides a guideline of manipulating light enhancement distribution by adjusting the relative etch depth between nanorod and truncated microdome structures.
Subjects
Solar cells
polarization
light-emitting diodes
hybrid surface structure
guided modes
radiation profiles
Type
thesis
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