Fabrication of nanocrystalline Cd(Zn, S)Se thin films for PV-application: An electrochemical approach

The design considerations of light-harvesting and energy-converting systems belong to one of the most highlighted fields in modern research. Recently, it has been pointed out that binary semiconducting materials with addition of one/or two or even more suitable elements provide a better prospect through their property engineering resulting in alloyed/multiphase compositions. We are presenting the synthesis and growth of CdSe and Cd1-xZnxSySe1-y (0 ≤ x = y ≤ 0.35) thin film using solution growth technique developed and made optimistic by us. The nature of the growth surface was determined by the contact angle measurements. The EDS analysis confirmed substitution of Cd by Zn and Se by S at high x and y concentrations. The structural determination using X-ray diffraction (XRD) analysis suggested formation of the polycrystalline films of hexagonal-wurtzite structure. The SEM observations showed a network of rhomboidal flower like crystallites transformed from an aggregated bunch of nano-sized globular grains as a result of addition of Zn and S in to CdSe. The electrode/electrolyte PV-cells were then formed with these films as photoelectrodes and a sulphide/polysulphide as an electrolyte (0.25 M) and investigated through the different electrical and optical characteristics in dark and under illumination. The maximum open-circuit photo voltage of 400 mV and a short circuit photocurrent of 0.166 mA/cm2 were obtained from a cell fabricated with an electrode composition of x = y = 0.075 (I/P illumination intensity is 13.4 mW/cm2). This resulted in the energy conversion efficiency of 3.18% and a fill factor of 64.1% respectively. The enhancement in PV-performance is explained adequately and supported by the changes in the electrode properties.