Deposition of CuInSe₂ by the hybrid sputtering and evaporation method

CuInSe₂ thin films deposited by a hybrid process combining magnetron sputtering of Cu and In with evaporation of Se have been analyzed and solar cells have been fabricated. The hybrid technique is shown to produce CuInSe₂ films of device quality. Heterojunction Mo/CuInSe₂/CdS/ITO/Ni devices with photovoltaic conversion efficiencies as high as 7.7% have been tested. Device characteristics for the best device include V_oc = 0.385 V, J_sc = 32.6 mA, and a fill factor of 61.3%. The device required an air anneal to achieve full efficiency. Results of microstructural analyses using transmission electron microscopy are reported. The results assist in determining what limits the performance of these devices. As-deposited CuInSe₂ exhibits no measurable differences as compared with CuInSe₂ produced by three-source evaporation. All films contain microtwins, stacking faults, and voids. No evidence was found for second phases in material with metal atom fractions as much as 4% off stoichiometry. Defect ordering produces features in the diffraction patterns of single-phase material at positions not normally allowed for the chalcopyrite structure. These measurements are compared with results for single crystals grown with the vertical Bridgeman method by Tomlinson (1986). X-ray photoelectron spectroscopy results characterizing the valence band as a function of film composition are also presented.