Comparative study of CdTe thin film solar cells with wet and dry CdCl<inf>2</inf> treatment process

Abstract

In this work, CdTe films were prepared by r.f. magnetron sputtering. Influence of conventional wet and dry CdCl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> treatments on the structural and optical properties of CdTe films were investigated by field emission scanning electron microscope (FE-SEM), x-ray diffraction (XRD), and UV-Visible spectrophotometer. Also, CdS/CdTe thin film solar cells were fabricated by all sputtering process and the cell characteristics were studied. The as-deposited CdTe thin films had a zincblende structure highly oriented with the (111) direction parallel to the substrate surface. The CdTe films lose their preferred orientation and become polycrystalline by heat treatment with dry CdCl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> treatment. The wet CdCl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> treatment exhibited a similar trend, but is less effective for grain growth than dry CdCl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> treatment. The photovoltaic properties of the CdS/CdTe solar cell were considerably improved with the increase in the annealing temperature, which was caused by the increase of grain size in CdTe films. However, the wet CdCl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> process was not suitable for reproducible fabrication.