The admittance technique was used in order to investigate the frequency dependence of dielectric constant (epsilon'), dielectric loss (epsilon aEuro(3)), dielectric loss tangent (tan delta), the ac electrical conductivity (sigma (ac)), and the electric modulus of PVA (Ni-doped) structure. Experimental results revealed that the values of epsilon' , epsilon aEuro(3), (tan delta), sigma (ac) and the electric modulus show fairly large frequency and gate bias dispersion due to the interface charges and polarization. The sigma (ac) is found to increase with both increasing frequency and voltage. It can be concluded that the interface charges and interfacial polarization have strong influence on the dielectric properties of metal-polymer-semiconductor (MIS) structures especially at low frequencies and in depletion and accumulation regions. The results of this study indicate that the epsilon' values of Au/PVA/n-Si with Nickel-doped PVA interfacial layer are quite higher compared to those with pure and other dopant/mixture's of PVA.