## Void formation on PERC solar cells and their impact on the electrical cell parameters verified by luminescence and scanning acoustic microscope measurements

2015
Job, Reinhart
Journal article
Published
##### Published in
Energy Procedia ; 84 (2015). - pp. 47-55. - eISSN 1876-6102
##### Abstract
Ideally formed local Al-contacts of passivated emitter and rear contact solar (PERC) cells feature an eutectic and an uniform local back surface field (LBSF). Under certain conditions the eutectic is missing after the co-firing process, referring to the well-known voids. So far light beam induced current (LBIC) measurements are used to obtain information concerning the passivation quality of the LBSF in local contacts in general. In addition, the destructive technique of scanning electron microscopy (SEM) is established for distinguishing whether a void features a sufficiently thick BSF-layer or a very thin/no BSF-layer. However, both methods are very time consuming.
This paper shows a non-destructive and fast characterization of solar cells by applying electroluminescence (EL) and photoluminescence (PL) measurements to investigate the effect on the electrical parameters after locating the voids by scanning acoustic microscopy (SAM). For filled contacts EL and PL measurements correlate well with the resulting values for series resistance (RS) and dark saturation current density (j0): the formed LBSF leads to a good surface passivation (high PL signal intensity, low value for j0) and the eutectic layer ensures a good electrical contact (high EL signal intensity, low value for RS). Voids with a sufficiently thick LBSF show a high PL signal intensity whereas the intensity is significantly reduced for a very thin or completely missing LBSF. Increased values for RS can be explained by the missing eutectic layer. In addition, the electrical connection of the LBSF to the paste can be derived from the value of RS.
530 Physics
##### Keywords
scanning acoustic microscopy; luminescence measurements; local Al-contact; void
##### Cite This
ISO 690HORBELT, Renate, Giso HAHN, Reinhart JOB, Barbara TERHEIDEN, 2015. Void formation on PERC solar cells and their impact on the electrical cell parameters verified by luminescence and scanning acoustic microscope measurements. In: Energy Procedia. 84, pp. 47-55. eISSN 1876-6102. Available under: doi: 10.1016/j.egypro.2015.12.294
BibTex
@article{Horbelt2015-12forma-33580,
year={2015},
doi={10.1016/j.egypro.2015.12.294},
title={Void formation on PERC solar cells and their impact on the electrical cell parameters verified by luminescence and scanning acoustic microscope measurements},
volume={84},
journal={Energy Procedia},
pages={47--55},
author={Horbelt, Renate and Hahn, Giso and Job, Reinhart and Terheiden, Barbara}
}

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<dcterms:abstract xml:lang="eng">Ideally formed local Al-contacts of passivated emitter and rear contact solar (PERC) cells feature an eutectic and an uniform local back surface field (LBSF). Under certain conditions the eutectic is missing after the co-firing process, referring to the well-known voids. So far light beam induced current (LBIC) measurements are used to obtain information concerning the passivation quality of the LBSF in local contacts in general. In addition, the destructive technique of scanning electron microscopy (SEM) is established for distinguishing whether a void features a sufficiently thick BSF-layer or a very thin/no BSF-layer. However, both methods are very time consuming.&lt;br/&gt;This paper shows a non-destructive and fast characterization of solar cells by applying electroluminescence (EL) and photoluminescence (PL) measurements to investigate the effect on the electrical parameters after locating the voids by scanning acoustic microscopy (SAM). For filled contacts EL and PL measurements correlate well with the resulting values for series resistance (R&lt;sub&gt;S&lt;/sub&gt;) and dark saturation current density (j&lt;sub&gt;0&lt;/sub&gt;): the formed LBSF leads to a good surface passivation (high PL signal intensity, low value for j&lt;sub&gt;0&lt;/sub&gt;) and the eutectic layer ensures a good electrical contact (high EL signal intensity, low value for R&lt;sub&gt;S&lt;/sub&gt;). Voids with a sufficiently thick LBSF show a high PL signal intensity whereas the intensity is significantly reduced for a very thin or completely missing LBSF. Increased values for RS can be explained by the missing eutectic layer. In addition, the electrical connection of the LBSF to the paste can be derived from the value of R&lt;sub&gt;S&lt;/sub&gt;.</dcterms:abstract>
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