The present invention provides a polymer-polyoxometalate composite ink, which comprises a solvent, a polymer or an intertwined structure with more than one polymer and a polyoxometalate, wherein a weight ratio of the polymer or the intertwined structure with more than one polymer to the polyoxometalate is in the range from 1:0.001 to 1:0.09. The said polymer-polyoxometalate composite ink could be configured to produce a carrier transport film and an organic electronic device comprising the carrier transport film.