JNS pyrolysis route has been successfully employed to grow CuO thin films at various substrate temperature, ranging from 300 to 600˚C. The XRD analyses revealed the monoclinic phased polycrystalline growth of the samples and exhibited the strong influence of the substrate temperature (ST) on the crystallite sizes. Optical transmission and bandgap studies also showed that sample bandgaps clearly rely upon the growth temperatures. The SEM micrographs displayed the agglomerated growth of particles having golf ball-like structures. The occurrence of Cu and O in the samples were confirmed through EDS analyses. The studies on DC electrical conductivities also shows strong dependency on the ST. A p-CuO/n-Si diode was fabricated at the ST of 600˚C and the diode parameters like barrier height ( ϕb ) and ideality factor (n) were determined under light and dark conditions.