Optical Evaluation Of Silicon Wafers With Rounded Rear Pyramids

Keywords

Light trapping; photoluminescence spectroscopy (PLS); ray tracing; solar cells; texture

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.

Publication Date

11-1-2017

Publication Title

IEEE Journal of Photovoltaics

Volume

7

Issue

6

Number of Pages

1596-1602

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1109/JPHOTOV.2017.2754060

Socpus ID

85031809794 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/85031809794

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