Sustainable Energy by Thin Film Photovoltaics

Cu(In,Ga)Se2 thin film solar cells show promise as a cost effective source of renewable energy. One approach to growing Cu(In,Ga)Se2 thin films is by reaction of a Cu-In-Ga metal precursor film in a selenium-containing atmosphere. In this work, precursors deposited by sputtering from a single Cu-In-Ga compound target were compared to precursors deposited by sequential sputtering from a CuGa alloy target and an In target. The objective is to determine if the single target deposition can provide better control of composition and improved reproducibility. The composition and morphology of the target and precursor were observed over a range of sputtering conditions to evaluate target stability and precursor reproducibility over time. Precursors were then selenized by reaction in hydrogen selenide to form Cu(In,Ga)Se2 films. These films were characterized by x-ray diffraction and scanning electron microscopy to study changes in phase and morphology of the films and good solar cell devices were fabricated from the films.