PVP-SiO2 and PVP-TiO2 hybrid films for dielectric gate applications in CdS-based thin film transistors

We report a simple solution process to deposit organic-inorganic poly (vinyl phenol) (PVP)–SiO2 and PVP-TiO2 hybrid films. The spin dropped hybrid films were prepared at low-temperature and their main properties were studied by TGA, FE-SEM, AFM, FTIR, XPS and contact angle measurements. The results show that the surface of the PVP-SiO2 and PVP-TiO2 hybrid films is smooth with very low surface roughness of 0.25 and 0.51 nm, and surface energy of 48.4 and 40.1 mJ/m2, respectively. The electrical properties of the hybrid films, measured on MIM devices, show low leakage current density under 10−7 A/cm2 and dielectric constant of 5 and 4.6 at 1 kHz, respectively. The hybrid films were used as gate dielectric in solution-processed CdS thin film transistors (TFTs), showing diverse performance. The CdS/PVP-SiO2 devices showed high mobility of 18 cm2/Vs, on/off current ratio of 104, low threshold voltage of 0.6 V and subthreshold swing of 0.25 V/dec. Whereas, the corresponding values for the CdS/PVP-TiO2 ones were 0.45 cm2/Vs, 104, 1.9 V and 1.25 V/dec, respectively. The lower electrical performance of the CdS/PVP-TiO2 devices was attributed to the mismatching surface energies between the surfaces of the dielectric and semiconductor layers, and to the influence of a large number of trapped charges at this interface. [Display omitted] •PVP-based organic-inorganic hybrid dielectric films processed at low temperature.•Hybrid materials with strongly linked phases.•Enhanced dielectric properties due to the SiO2 and TiO2 inorganic phases.•TFTs with hybrid dielectric gate prepared at low temperature.•Completely solution-processed CdS-based TFTs.