R.F. Sputtered CuInSe2 Thin Films for Photovoltaic Applications

In the past work the achievement of an all sputtered CuInSe2/CdS thin film solar cell with an efficiency around 5% has been described. Here the first results, concerning the preparation of the CuInSe2 film by depositing an "In-rich" layer on top of a "Cu-rich" layer are reported. Films of different stoichiometry have been obtained by using several targets in which the Cu/In ratio has been varied between 0.66 and 1.2. For the first time, a Zn0.15Cd0.85S film, deposited by R. F. sputtering in an Ar/H2 atmosphere, has been used as a window. Solar cells prepared by using a CuInSe2 double layer as an absorber has shown so far an efficiency not larger than that obtained by using a single layer. This seems to be due to the fact that the interaction between the top and bottom layer facilitates the segregation of foreign phases like CU2Se, which could be present in the bottom layer. Therefore, in order to increase the efficiency of the sputtered CuInSe2/ZnCdS thin film solar cells a bottom layer free of foreign phases needs to be used.