Graduation Year

2004

Document Type

Thesis

Degree

M.S.E.E.

Degree Granting Department

Electrical Engineering

Major Professor

Ferekides, Chris S.

Keywords

vaporization, cadmium sulfide, post-deposition heat treatment, annealing, fill factor

Abstract

Polycrystalline CdS/CdTe thin film solar cells are among the leading candidates for low-cost, large scale terrestrial photovoltaic applications. CdTe has a high absorption coefficient and it can absorb the radiant energy within less than 2 (Mu)m of thickness. This makes it suitable for thin film applications. CdTe has a band gap of 1.45 eV at room temperature, which is nearly optimum for photovoltaic conversion efficiency under the AM 1.5 solar spectrum. The theoretical maximum efficiency for CdTe solar cells is 29%. However, to-date the experimental value is in the 16 % range. In most cases CdTe cells are subjected to a post-growth heat treatment which involves annealing in the presence of CdCl₂. The treatment results in significant increases in conversion efficiency (Eta) and all three solar cell parameters Voc, FF, and Jsc.

In this work, several variations of the CdCl₂ treatment were used on more than 100 samples to investigate their effects on the solar cell parameters. A vapor CdCl₂ method was applied for the treatment with various source temperatures, substrate temperatures, and treatment times. The cells were characterized by dark and light J-V and spectral response (SR) measurements.

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