Optical Evaluation of Silicon Wafers With Rounded Rear Pyramids
Date
2017
Authors
McIntosh, Keith
Zin, Ngwe Soe
Nguyen, Hieu
Stocks, Matthew
Franklin, Evan
Fong, Kean
Kho, Teng
Chong, Teck
Wang, Er-Chien
Ratcliff, Tom
Journal Title
Journal ISSN
Volume Title
Publisher
IEEE
Abstract
We investigate the light trapping in Si wafers that are textured with conventional random pyramids on their front surface and rounded random pyramids on their rear. It is well established that rounding the pyramids leads to better surface passivation, but whether or not it improves light trapping depends on the cell structure. In this paper, we apply ray tracing, spectrophotometry, and photoluminescence spectroscopy (PLS) to understand and quantify how rounding the rear pyramids might affect the light trapping in back-contact solar cells. We describe how rounding the pyramids leads to two competing optical effects: 1) reduced absorption in the rear films and 2) reduced scattering from the rear texture. The first effect improves light trapping whereas the latter degrades it. We show how the influence of each effect depends on wavelength and how they can be discerned (but not easily quantified) in reflectance curves. With PLS measurements, we conclude that for our sample structure and etch solution, the generation current is approximately constant for etch durations less than ~60 s, and decreases significantly as the etch duration increases. Thus, by limiting the duration of the rounding etch, superior surface passivation can be attained without degrading the light trapping.
Description
Keywords
Citation
Collections
Source
IEEE Journal of Photovoltaics
Type
Journal article