Temperature dependent photoluminescence study on ZnO/Graphene nanocomposite films

•Fabrication of ZnO/graphene composite films, in which graphene oxide nanoplatelets (∼2 nm thick) are embedded in nanograined ZnO (∼30 nm in grain size) from colloidal suspensions of graphene oxide with an aqueous zinc precursor by Ultrasonic-assisted spray pyrolysis (UASP).•Observation of both free and defect-mediated excitonic emissions from temperature-dependent PL study on ZnO/G-O nanocomposite.•New graphene-related transition was observed at 372 nm (3.33 eV) along with the exciton transition bound to neutral acceptors or deep donors.

We report observation of both free and defect-mediated excitonic emissions from temperature-dependent PL study on ZnO/graphene oxide (G-O) nanocomposite grown by ultrasonic assisted spray pyrolysis (UASP). From the temperature-dependent photoluminescence (PL) spectra of the ZnO/G-O nanocomposite, new graphene-related peak was observed at 372 nm along with the exciton transition bound to neutral acceptors or deep donors. The PL intensity of new graphene-related peaks (3.33 eV) become more prominent with increasing G-O concentration, and it was saturated or decreased with the addition of >7.0 wt% of G-O. This feature indicates that new graphene-related states were created below conduction band of ZnO, which supports the excitonic PL enhancement by graphene-embedding is contributed not by charge transfer, but by vacancy filling effect of G-O.