Order-disorder transformations and the nature of the copper-suphide layer in CuxS/CdS solar cells

The evidence that the two copper–sulphide phases, chalcocite and djurleite, can exist at the same compositions near Cu2S is briefly reviewed. Experimental data suggest that djurleite is the more stable phase at room remperatures and that a polymorphic chacocite→djurleite transformation may take place in the thin copper–sulphide layers present in solar cells. The kinetics of this transformation are discussed and related to low–temperature phase equilibria in the Cu/S systems around Cu2 S2 and to the processes that may operate in solar cells.