Understanding the Path to Contact Silicon Solar Cells with 140 Ω/sq High Resistance Emitters

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Ren, K. (2019). Understanding the Path to Contact Silicon Solar Cells with 140 Ω/sq High Resistance Emitters. Unc Charlotte Electronic Theses And Dissertations.
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Abstract

Solar cell electricity can only be attractive if it is cost effective. In order for it to be affordable, the cost of manufacturing the solar cell must be decreased. Both material use and improved efficiency should be addressed in order to realize this goal. One of the paths to improve efficiency is to fabricate the cells on lowly doped emitters, which is difficult to contact with the present screen-printing technology. In this thesis work, the study of the microstructure of the Ag gridline/Si interface was carried out to elucidate the elemental composition of the glass layer underneath this contact. SEM, EDS and Raman Spectrometer were used to analyze two cells (one each) made with two different paste samples. The SEM showed that the worse cell had very thick glass layer underneath the metal contact. This cell also showed very high contact resistance and low fill factor (FF). Upon the removal of the metal contact and the glass layer, the Ag crystallites in the Si emitter were less compared to the better cell with low contact resistance and high FF. The EDS confirmed that the existence of Al, Pb, Te, Ag and Bi in the glass but not in the Si emitter. This was confirmed by the Raman spectra with the peaks that aligned with some compounds of Pb and Te. This showed that the glass layer contains some alloys of Pb and Te and these alloys tend to increase its conductivity and decrease the contact resistance. It can therefore be inferred that, the glass layer increased conductivity in conjunction with the Ag crystallites embedded in Si emitter will lead to an optimized contact on the lowly doped emitter.

Details
Author

Ren, Keming

Title

Understanding the Path to Contact Silicon Solar Cells with 140 Ω/sq High Resistance Emitters

Physical Description

1 online resource (47 pages) : PDF

Date

2019

Degree Granting Institution

University of North Carolina at Charlotte

Abstract

Solar cell electricity can only be attractive if it is cost effective. In order for it to be affordable, the cost of manufacturing the solar cell must be decreased. Both material use and improved efficiency should be addressed in order to realize this goal. One of the paths to improve efficiency is to fabricate the cells on lowly doped emitters, which is difficult to contact with the present screen-printing technology. In this thesis work, the study of the microstructure of the Ag gridline/Si interface was carried out to elucidate the elemental composition of the glass layer underneath this contact. SEM, EDS and Raman Spectrometer were used to analyze two cells (one each) made with two different paste samples. The SEM showed that the worse cell had very thick glass layer underneath the metal contact. This cell also showed very high contact resistance and low fill factor (FF). Upon the removal of the metal contact and the glass layer, the Ag crystallites in the Si emitter were less compared to the better cell with low contact resistance and high FF. The EDS confirmed that the existence of Al, Pb, Te, Ag and Bi in the glass but not in the Si emitter. This was confirmed by the Raman spectra with the peaks that aligned with some compounds of Pb and Te. This showed that the glass layer contains some alloys of Pb and Te and these alloys tend to increase its conductivity and decrease the contact resistance. It can therefore be inferred that, the glass layer increased conductivity in conjunction with the Ag crystallites embedded in Si emitter will lead to an optimized contact on the lowly doped emitter.

Genre

masters theses

Subjects--Topics

Electrical engineering

Degree

M.S.

Keywords

Ag2te
Ag Paste
Contact Resistance
Pbte
Si Solar Cells

Subject Area

Electrical Engineering

Advisor(s)

Ebong, Abasifreke

Committee Members

Zhang, Yong
Stokes, Ed

Degree Note

Thesis (M.S.)--University of North Carolina at Charlotte, 2019.

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Rights Holder Information

Copyright is held by the author unless otherwise indicated.

Identifier

Ren_uncc_0694N_12078

Permalink

http://hdl.handle.net/20.500.13093/etd:1998