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Crystallographic and optical properties of narrow band gap Cu 2 GeSe 3 and Cu 2 (Sn 1− x Ge x )Se 3 solid solution

2014; Institute of Physics; Volume: 53; Issue: 5S1 Linguagem: Inglês

10.7567/jjap.53.05fw06

1347-4065

Masaru Morihama, Tsuyoshi Maeda, Issei Yamauchi, Takahiro Wada,

Copper-based nanomaterials and applications

Cu2GeSe3 (CGSe) was synthesized by mixing elemental powders and post-heating at 600 °C in N2 gas. The X-ray diffraction pattern of the synthesized CGSe agreed with that of the simulated monoclinic structure. Characteristic diffraction peaks of 110 and 021 for the monoclinic structure were clearly observed. CGSe's crystal structure was characterized by Rietveld refinement of the powder X-ray diffraction data. CGSe has a monoclinic crystal structure with the space group of Cc (No. 9), and the refined lattice parameters were a = 6.7378 Å, b = 11.820 Å, c = 6.7505 Å, and β = 108.42°. The band gap of Cu2GeSe3 was determined to be 0.78 eV by the diffuse reflectance spectra of the powder. The Cu2(Sn1−xGex)Se3 (CTGSe) solid solution with 0 ≤ x ≤ 1.0 powders were also synthesized, and their crystal structures were characterized by Rietveld refinement of the powder X-ray diffraction data. Lattice constants a, b, and c were linearly decreased from Cu2SnSe3 (a = 6.873 Å, b = 12.008 Å, c = 6.921 Å, and β = 109.19°) to CGSe with increasing Ge content. The preliminary fabricated Cu2(Sn0.6Ge0.4)Se3 solar cell showed an efficiency of 2.43%, with a Voc of 334 mV, a Jsc of 20.4 mA/cm2, and an FF of 35.5%.