Study of difluorochloromethane activation treatment on low substrate temperature deposited CdTe solar cells

In this paper we describe a low substrate temperature CdTe fabrication process by vacuum evaporation (VE) where the recrystallization step avoids the use of CdCl2, which is a carcinogenic material. In our process CdS and CdTe are deposited at pressures of 10−6 mbar in the same chamber by thermal evaporation and with substrate temperature of 150 °C and 340 °C, respectively. The CdTe/CdS/TCO stacks are then put in a quartz chamber and, after having previously pumped the chamber down to 10−5 mbar, a controlled mixture of argon and chlorine containing gas is fluxed with a substrate temperature in a range between 400 °C and 450 °C. The morphological properties of the single layers are studied by X-ray diffraction (XRD), atomic force microscopy (AFM), cathodo-luminescence (CL) and the electrical properties of the finished devices are presented by means of current–voltage (I–V) and capacitance–voltage (C–V) measurements.

► CHClF2 and CdCl2 treatments on low temperature grown CdTe devices are compared. ► Morphology and crystal structure of treated CdTe layers are shown. ► Electrical properties of CHClF2 treated CdTe are studied by C–V and DLCP. ► Electrical properties of CHClF2 treated CdTe by PVD and CSS are compared. ► Differences of CdCl2 and CHClF2 treated low temperature grown CdTe are presented.