The present invention relates to a method of depositing a coating comprising zinc oxide on a substrate; to a chemical vapour deposition precursor mixture for use in same and to a coated glass article and a photovoltaic cell prepared with a zinc oxide coating prepared using the method which comprises: providing a substrate, providing a precursor mixture comprising an alkyl zinc compound and a phosphorus source, the phosphorus source comprising a compound of formula OnP(OR)3, wherein n is 0 or 1 and each R is hydrocarbyl, and delivering the precursor mixture to a surface of the substrate.