Study Of Cu Free Back Contacts To Thin Film CdTe Solar Cells

Author

Vijay Viswanathan, University of South Florida

Graduation Year

2004

Document Type

Dissertation

Degree

Ph.D.

Degree Granting Department

Electrical Engineering

Major Professor

Christos. S. Ferekides, Ph.D

Committee Member

Don Morel, Ph.D

Committee Member

Richard Gilbert, Ph.D

Committee Member

Y.L. Chiou, Ph.D

Committee Member

Sarath Witanachchi, Ph.D

Keywords

CdTe, Contacts, Ni-P, ZnTe, Dry Etching, Stability

Abstract

The goals of this project are study Cu free back contact alternatives for CdS/CdTe thin film solar cells, and to research dry etching for CdTe surface preparation before contact application. In addition, an attempt has been made to evaluate the stability of some of the contacts researched. The contacts studied in this work include ZnTe/Cu₂Te, Sb₂Te₃, and Ni-P alloys.

The ZnTe/Cu₂Te contact system is studied as basically an extension of the earlier work done on Cu₂Te at USF. RF sputtering from a compound target of ZnTe and Cu₂Te respectively deposits these layers on etched CdTe surface. The effect of Cu₂Te thickness and deposition temperature on contact and cell performance will be studied with the ZnTe depositions conditions kept constant. C-V measurements to study the effect of contact deposition conditions on CdTe doping will also be performed. These contacts will then be stressed to high temperatures (70-100 degrees C) and their stability with stress time is analyzed.

Sb₂Te₃ will be deposited on glass using RF sputtering, to study film properties with deposition temperature. The Sb₂Te₃ contact performance will also be studied as a function of the Sb₂Te₃ deposition temperature and thickness. The suitability of Ni-P alloys for back contacts to CdTe solar cells was studied by forming a colloidal mixture of Ni₂P in graphite paste. The Ni-P contacts, painted on Br-methanol etched CdTe surface, will be studied as a function of Ni-P concentration (in the graphite paste), annealing temperature and time. Some of these cells will undergo temperature stress testing to determine contact behavior with time.

Dry etching of CdTe will be studied as an alternative for wet etching processes currently used for CdTe solar cells. The CdTe surface is isotropically etched in a barrel reactor in N₂, Ar or Ar:O₂ ambient. The effect of etching ambient, pressure, plasma power and etch time on contact performance will be studied.

Scholar Commons Citation

Viswanathan, Vijay, "Study Of Cu Free Back Contacts To Thin Film CdTe Solar Cells" (2004). USF Tampa Graduate Theses and Dissertations.
https://digitalcommons.usf.edu/etd/1285