Progress towards 14% efficient CdTe solar cells in substrate configuration

CdTe solar cells are conventionally grown in superstrate configuration. However, the growth in substrate configuration offers more control of junction properties as recrystallization of CdTe and junction formation with CdS can be decoupled. In this paper the influence of various annealing treatment conditions of the CdS layer on its morphology and phase and on the device properties is presented. The presence of CdCl₂ during this annealing treatment is important for the phase change of the CdS layer to hexagonal wurtzite and for high efficiencies. A CdCl₂ treatment of the CdS at 360 °C improves the efficiency of the device without the adverse effect of pinhole formation in the CdS. CdTe solar cells in substrate configuration with more than 13% efficiency are achieved as a progress towards 14% efficiency.