Study of CdS/CdTe solar cells activated with N-O<inf>2</inf>-CHClF<inf>2</inf> gas mixture

Abstract

The activation process is an important step for fabricating CdTe based solar cells. In this work, it was made by using Argon-CHClF 2 , Argon-Oxygen-CHClF 2 and Nitrogen-Oxygen-CHClF 2 gas mixtures. Solar cells with 12.0% of efficiency for 1 cm2 were obtained when it is activated by using Nitrogen-Oxygen-CHClF2 gas mixture. We show that Nitrogen also plays an important role for improving the solar cell efficiency. The solar cell reported in this work were fabricated using ZnO/CdS/CdTe layers grown onto commercial ITO used as TCO. Both ZnO and CdS thin films were deposited using rf-sputtering. The first one is working as a buffer layer. The CdS is deposited in Argon atmosphere and it is not intentionally treated before depositing CdTe thin film with 8 µm thickness by the conventional CSS technique. The cell uses a simple sputtered Cu (5nm)/Mo (750nm) back contact. Illuminated and darkness J-V curves, HR-SEM images before and after the activation process are presented. The effect of the gas mixtures on the parameters of the CdS/CdTe solar cell is discussed.