| SM ISO690:2012|
GURIEVA, Galina; LEVCENKO, Sergiu; CORREIA DE SOUSA, A. Pereira; UNOLD, T.; SCHORR, S.. Investigation of detection limits of ZnSe and Cu2SnSe3 secondary phases in Cu2ZnSnSe4. In: Materials Science and Condensed Matter Physics. Editia a 8-a, 12-16 septembrie 2016, Chişinău. Chişinău: Institutul de Fizică Aplicată, 2016, p. 265. ISBN 978-9975-9787-1-2.
|Materials Science and Condensed Matter Physics
Editia a 8-a, 2016
Conferința "International Conference on Materials Science and Condensed Matter Physics" |
8-th Edition, Chişinău, Moldova, 12-16 septembrie 2016
Quaternary Cu2ZnSnSe4 (CZTSe) is a promising semiconductor material for absorber layer in thin film solar cells due to direct band gap around 1 eV and high absorption coefficient (> 104 cm-1) . The highest conversion efficiency of CZTSe solar cells is above 11% . Nevertheless, a low open circuit voltage with respect to the band gap is a common phenomenon in CZTSe photovoltaic devices. A plausible reason for this is a reduction in the effective band gap due to inhomogeneities in structure, phase, or composition. To gain a detailed knowledge of the influence of phase inhomogeneities on the performance of solar cells, the understanding of detection limits of conventionally used characterization methods is essential. The aim of this work is to study the limits of the sensitivity of X-ray diffraction and Raman spectroscopy to the presence of two very common secondary phases for Cu2ZnSnSe4– ZnSe and Cu2SnSe3. Polycrystalline powder of two CZTSe samples (slightly Zn-rich) and Cu2SnSe3 sample have been grown using the solid state reaction method in evacuated silica tubes. Additionally, an industrially produced powder of ZnSe have been used to produce a number of mixtures of corresponding CZTSe with 1%, 2%, 3%, 5%, 10% and 20% of ZnSe or Cu2SnSe3 respectively. The structural characterization of the starting materials as well as of mixtures was carried out by powder X-ray diffraction (PXRD) and subsequent Rietveld analysis of the diffraction data using the FullProf suite . Rietveld refinement of diffraction data of the mixtures was performed, paying a special attention to the influence of amounts of ZnSe and Cu2SnSe3 on the diffraction patterns of the mixtures. The amounts of secondary phases determined by Rietveld refinement have been compared with the initial data, determining in this way the detection limits of PXRD for these secondary phases. To study the crystal structure of the synthesized mixtures at the micrometer scale Raman spectroscopy has been employed. In these measurements a 632.8nm laser line was employed and it was found to be efficient for both ZnSe and Cu2SnSe3 phase detection. By performing Raman line scan measurements we evaluated characteristic Raman mode intensities corresponding to the different phases and thus are able to estimate the mixture composition.