A comparative study of Cu_2ZnSnS_4 thin films growth by successive ionic layer adsorption-reaction and sol-gel methods

摘要

Owing to the high natural abundance and non-toxicity of all the constituents, the copper-zinc-tin-sulfide compound has been attracting attention in recent years for the production of cheap solar absorber materials. Solution-based low-cost approaches are being developed for the deposition of this compound. In this comparative study, we have investigated Cu_2ZnSnS_4 thin films prepared by using successive ionic layer adsorption-reaction and sol-gel methods. X-ray diffraction studies indicated the polycrystalline nature of the films. No secondary phases were observed. The sol-gel grown Cu_2ZnSnS_4 film was found to have smaller crystallite size and higher micro-strain and dislocation density values. Phase purity and good crystalline quality of the studied films were proved through the Raman studies. From the scanning electron microscopy images, sol-gel grown Cu_2ZnSnS_4 film was found to have more homogenous and smooth morphology. Possible chemical formula of the films was determined. The optical absorption of the sol-gel grown film covered a wider wavelength range by means of absorbing more visible photons. The optical band gap values were estimated to be 1.45 and 1.40 eV for the successive ionic layer adsorption-reaction and sol-gel grown samples, respectively. It was concluded that both methods are effective and can be used to produce high-quality Cu_2ZnSnS_4 thin films for cheap and green solar cell applications.