Enhancement in the photoluminescence, linear and third order nonlinear optical properties of nanostructured Na-CdS thin films for optoelectronic applications

Cadmium sulphide (CdS) thin films are widely used for various devices applications. Here, we report on the development of nanostructured CdS and Na-CdS thin films with enhanced optical and emission properties using an inexpensive deposition method. High quality Na-CdS nanocrystalline films were fabricated using spin coating method on glass substrates with different doping concentration (1–4 wt%). X-ray diffraction studies of the prepared films reveal a cubic zinc blende structure. The crystallites sizes of the films were found to be about ~ 5–11 nm and significantly increase with increasing Na doping concentrations. Morphological imaging of the grown films shows spherical nano-size grains in the range of 9–27 nm. The nanocrystalline films show high transmittance (~ 85%) in the visible region and was found to increase with increasing Na doping content. Room temperature photoluminescence (RTPL) spectra of the films reveal a direct band to band transition with enormous amount of enhancement in near band emission (NBE) up to 400% for the films doped with 1 and 2 wt% Na concentrations which is about ten times higher as compared with pure CdS films. A good improvement was also observed with Na doping in the linear and third order nonlinear optical properties of the films. The reported results in the current study show the high potential of Na-doped CdS films as candidates for low cost high performance optoelectronic devices.