Cu(InAl)Se/sub 2/ thin films and devices deposited by multisource evaporation [solar cells]

Cu(InAl)Se/sub 2/ is investigated as an alternative high bandgap alloy of CulnSe/sub 2/ for achieving devices and modules with greater performance as bandgap and V/sub OC/ increase. Device efficiencies with Cu(InGa)Se/sub 2/ and CuIn(SeS)/sub 2/ decrease for bandgap greater than 1.3 eV. In this work, Cu(InAl)Se/sub 2/ thin films were deposited by four-source elemental evaporation with a composition range of 0/spl les/Al/(In+Al)/spl les/0.65 corresponding to a bandgap range 1.0/spl les/E/sub g//spl les/1.8 eV. All films are single phase as determined by X-ray diffraction. Characterization of optical and structural properties of the films shows that the effect of increasing Al content on bandgap and lattice spacing agrees with the results on Cu(InAl)Se/sub 2/ crystals and with calculated values. Solar cells with structure glass/Mo/Cu(InAl)Se/sub 2//CdS/ZnO were fabricated. The best cells have 11% efficiency and V/sub OC/ increases with increasing Al content to greater than 0.7 V.