Browsing by Author "Ranjbar, Samaneh"
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- Effect of selenization conditions on the growth and properties of Cu2ZnSn(S,Se)4 thin filmsPublication . Ranjbar, Samaneh; Rajesh Menon, M.R.; Fernandes, P.A.; Cunha, A.F. daThe opto-electronic properties of copper zinc tin sulfide can be tuned to achieve better cell efficiencies by controlled incorporation of selenium. In this paper we report the growth of Cu2ZnSn(S,Se)4 (CZTSSe) using a hybrid process involving the sequential evaporation of Zn and sputtering of the sulfide precursors of Cu and Sn, followed by a selenization step. Two approaches for selenization were followed, one using a tubular furnace and the other using a rapid thermal processor. The effects of annealing conditions on the morphological and structural properties of the films were investigated. Scanning electron microscopy and energy dispersive spectroscopy were employed to investigate the morphology and composition of the films. Structural analyses were done using X-ray diffraction (XRD) and Raman spectroscopy. Structural analyses revealed the formation of CZTSSe. This study shows that regardless of the selenization method a temperature above 450 °C is required for conversion of precursors to a compact CZTSSe layer. XRD and Raman analysis suggests that the films selenized in the tubular furnace are selenium rich whereas the samples selenized in the rapid thermal processor have higher sulfur content.
- On the properties of Cu2ZnSn(S,Se)4 thin films prepared by selenization of binary precursors using rapid thermal processingPublication . Menon, M R Rajesh; Ranjbar, Samaneh; Sousa, M G; Fernandes, P A; Cunha, A F daCu2ZnSn(S,Se)4 thin films were grown on molybdenum coated glass substrates by selenization of stacked precursor layers of zinc, tin disulfide and copper sulfide. Selenization was performed using a rapid thermal processor at maximum temperatures in the range of 400°C to 550°C and at heating rates of 1°C/s and 2°C/s. The compositional, morphological and structural characterization of the films was carried out using energy dispersive x-ray spectroscopy, scanning electron microscopy, x-ray diffraction and Raman spectroscopy. X-ray diffraction and Raman scattering analysis suggests the formation of Cu2ZnSn(S,Se)4 only at lower temperatures, whereas Cu2ZnSnSe4 was formed at higher temperatures regardless of the heating rate used. Compositional analysis revealed that the films were Zn-poor and Sn-rich. However, the samples approach a near stoichiometric composition due to the loss of tin at a selenization temperature and heating rate of 550°C and 2°C/s, respectively. Large grains with an average lateral dimension of 4.5μm were observed for films prepared at these conditions which are very desirable for an absorber for solar cells.