Near infrared transparent conducting cadmium oxide deposited by MOCVD

Abstract

Polycrystalline cadmium oxide has been deposited on to glass substrates for use as transparent conducting oxides for thin film photovoltaics. The films were deposited by metal organic chemical vapour deposition (MOCVD). The oxygen precursor was tertiary butanol, which was chosen to avoid the pre-reaction often seen for more reactive oxygen sources when combined with the cadmium source, dimethylcadmium. This combination of precursors promoted a surface reaction to yield high quality CdO films with large grain size. The cadmium oxide, deposited at 280 °C, yielded a minimum resistivity of 3.9 × 10 − 4 Ω cm whilst maintaining an average transmittance between 450 and 2500 nm of 80%. This exceptional near-IR transmittance coupled with good electrical conduction is well suited to match the infrared requirements of multi-junction photovoltaics designed to capture greater proportions of the solar spectrum.