Tetrahedrite (Cu12Sb4S13) thin films for photovoltaic and thermoelectric applications. (1st November 2018)

• Record Type: Journal Article
• Authors: Prem Kumar, D.S.; Ren, Minqin; Osipowicz, Thomas; Mallik, Ramesh Chandra; Malar, P.
• Is Part Of: Solar energy. Volume 174(2018)
• Page Start: 422
• Page End: 430
• Publication Date: 2018-11-01
• Subjects: EBPVD -- Tetrahedrite -- Transport properties -- Optical absorption; Solar energy -- Periodicals; Solar engines -- Periodicals; 621.47
• DOI: 10.1016/j.solener.2018.08.080
• Languages: English
• ISSNs: 0038-092X

Abstract

Highlights: E-beam deposition of Cu12 Sb4 S13 thin films using mechanically alloyed single source material. ∼40–50 mA e-beam current is found optimal for Cu12 Sb4 S13 phase formation. RBS and PIXE studies are used to determine composition of the films. Optical band gap value of ∼1.8 eV with absorption coefficient of ∼10 5 cm −1 is observed for near stoichiometric films. Thermoelectric measurements shows the maximum power factor of 2.30 μW/cm-K 2 at 495 K for Cu12 Sb4 S13. Abstract: In this paper we have demonstrated the growth of Cu12 Sb4 S13 thin film through e-beam evaporation from a single source. The source material was pre-synthesised via ball mill method starting from a stoichiometric mixture of elements (Cu, Sb and S) taken in the atomic ratio of 12:4:13. The films were deposited at different beam currents viz. 40, 50 and 60 mA. The bulk material and thin films were studied using X-ray diffraction (XRD) and Raman spectroscopy to evaluate phase formation. The films grown at beam current values of 40 mA showed the presence of Cu12 Sb4 S13 phase along with Cu3 SbS4 and CuS secondary phases. The films grown at 50 mA and 60 mA are showing Cu3 SbS4 phase as main phase. These results are in agreement with the Raman studies. The composition of as grown films was analysed using Rutherford backscattered spectrometry (RBS) and proton induced X-ray emission (PIXE) measurements. The Cu content in the films is decreasing with increase in the beam current, whereas the Sb and S content shows increment. The optical absorption measurement was used to determine the optical band gap. The films show a direct band gap value of ∼1.8 eV with an optical absorption coefficient of ∼10 5 cm −1 . Temperature dependant Seebeck coefficient and electrical resistivity values were measured for the thin films and the power factor values were calculated. The positive Seebeck coefficient values obtained indicate p-type semiconducting nature of the films. The maximum power factor of 2.30 μW/cm-K 2 at 495 K was obtained for films grown at 40 mA e-beam current. The electrical and optical properties are significantly influenced by the presence of secondary phases and compositional deviation.