A study of CuGaSe2 thin film growth from multilayered precursors

In the growing process of CuGaSe2 thin films for solar cells, a bilayered GaSe/CuSe structure has been widely used as a precursor and characteristic of the bilayered precursors which have been studied in many research groups. It is well known that interdiffusion of Cu and Ga by concentration difference is a prerequisite for growing CuGaSe2 films from the GaSe/CuSe precursor. In the interdiffusion process, it is considered that the thinner each precursor layer is, the smaller activation energy and time needed to form the single phase CuGaSe2. In this study, the comparison of CuGaSe2 thin films from the multilayered precursor and the bilayered precursor was focused on in order to confirm the multilayered precursor to be a promising candidate for obtaining the single phase CuGaSe2 thin films. These results show that the CuGaSe2 pathway is dependent on the precursor structure. A bilayer precursor stack reveals that a phase transition from CuSe to CGS single phase accompanied by the growth of CuSe(006) plane and Cu2-xSe (111). However, GaSe/CuSe precursors do not show any intermediate phase transformations for the 4 and 6 sequences.

► Preparation of various of GaSe/CuSe precursors by using a co-evaporation method.
► Phase transition observation of precursor by using in situ HT-XRD.
► Multilayered precursors do not show any intermediate phase during annealing.