Preparation And Properties Of ZnO-Graphene Composite Thin Films On Flexible Substrates

Zinc oxide(Zn O)is an ?-? semiconductor compound with a wide and direct band gap.It has good optical and optoelectronic properties.Graphene is a new type of two-dimensional carbon semiconductor material with zero band-gap,which exhibits very unique electrical,mechanical and optical properties.ZnO-graphene compound is a new type of materials combining of the attractive properties of the both ZnO and graphene.In this paper,ZnO thin films were grown on flexible PET substrates using a hydrothermal method.Using a single variable method,ZnO thin films were prepared by changing hydrothermal conditions such as the growth concentration,the reation temperature and the growth time.The structure,morphology and optical properties of ZnO thin films were characterized by using XRD,SEM and PL.The optimal preparation parameters were summarized.The experimental results indicate that when growth time is 3 h,growth concentration is 0.03 mol/L and reaction temperature is 90 ?,the preparation conditions are optimal.Under this condition,ZnO nanorods array has great crystallinity and the average transmittance of ZnO film is more than 90 % under 400-800 nm.The grapheme oxide film was prepared on PET substrates by a dip-coating method,and reduced by using HI acids to obtain graphene film.The graphene film exhibits sheet resistance of 15.2 k?/sq and transparencies of 85.95 %.ZnO-graphene composite thin films were successfully prepared by hydrothermal method.Without seed layers,flower-like ZnO-graphene composite films were prepared by a direct hydrothermal method.The results show that compared with the pure ZnO film,flower-like ZnO in composite films grow mainly along(100)plane.And the ultraviolet photoluminescence intensity of flower-like ZnO-graphene composite films is significantly enhanced due to the couling between the PL photons from ZnO and the graphene surface plasmon.With seed layers,ZnO nanorods array-graphene composite films were prepared.The results indicate that the presence of the seed layers make ZnO nanorods preferentially oriented along the c axis.And compared compared with the pure ZnO film,the fluorescence intensity of ZnO nanorods array-graphene composite film is decreased because graphene in composite films can effectively transfer the photo electrons to reduce the recombination probability of photogenerated electrons-hole pairs of ZnO.