Barrier Height Measurement of Cadmium Telluride (CdTe) Solar Cells

Among the thin film generation, the Cadmium Telluride (CdTe) solar cell is favored for research because it has a low cost and a relatively high efficiency (22.1% in 2016). However, its efficiency is still lower than the theoretical limit. One major problem is at the back-contact junction. Since CdTe solar cells have a high electron affinity (about 4.5 eV), typical back contacts such as metals fail to create good ohmic contacts and as a result a Schottky barrier is formed at the back-contact junction. The Schottky barrier affects charge carrier collections and lowers the efficiency of the cell.

In this work, we show our studies on the effect of the barrier height on the performance of CdTe solar cells. We tested CdTe cells with different back contacts and found they had different characteristics and efficiencies. Using the turning point technique, we were able to obtain the barrier heights at the back-contact junction using the current-voltage characteristics of the solar cells at various temperatures. Our results showed that there is a correlation between the barrier height and cell performance: the lower the barrier height, the better the cell performed. These results yielded parameters that will aid us in choosing a superior back contact material for CdTe solar cells.