| As a novel green and renewable energy, the solar energy is a breakthrough of solving the energy crisis. CuInTe2(CIT) belongs to the I-III-VI2 ternary compound semiconductors, which possess certain unique characteristics. CIT is a direct band gap semiconductor with narrow band gap 0.91-1.0eV. Compared to some other narrow band-gap semiconductors such as CdS, there is no polluting element in CIT. Besides, both CIT and Cu(In, Ga)Se2 (CIGS) belong to chalcopyrite family, forming good lattice match. This kind of absorber is essential to bottom cells for multi-junction solar cells. As a result, CIT is one of the most promising semiconductors for solar cells.Compounds with rare earth ion are good candidates for optical materials because of the special structure of 4f energy level in rare earth element. This paper discussed rare earth doped semiconductor materials CuIn1-xRxTe2(R=La, Ce, Pr, Nd, Sm, Eu, Gd; x=0-0.3) (CIRT) which were synthesized by vacuum arc melting and vacuum solid state reaction in a muffle furnace. And the CIRT particles were prepared in a planetary ball mill. The phase structures and surface morphology of the samples were characterized by X-ray diffraction and field emission scanning electron microscopy. The composition ratio was measured by chemical composition analysis and energy dispersive spectroscopy. The lattice vibrations were detected by Raman scattering spectroscopy. The influence of rare earth elements and their concentrations on surface morphology and crystal structure was discussed by PDF cards, TREOR program and Rietveld structure refinement technology.The results show that single phases of CuIn1-xRxTe2 (x=0-0.2) have been successfully synthesized.There were small deviations from the ideal compositions, and phenomena of Poor-tellurium and rich-copper can also be detected in all the samples, indicating the element Te evaporation easily. The grain growths exhibit inhomogeneity from small bulks to large ones with grain size ranging from 5 micrometer to 20 micrometers. The grain surface morphologies reveal the evolutions of surface growth for the grains from the initial cylindrical and layer structures with smooth and uniform to the large granularity with sharp edges and triangle facet. The bulk grains initially pack with layer structures. The Rietveld refinement results showed the space group of CIRT was I-42d and the structure of the samples was chalcopyrite. In a unit cell, Cu resides in site 4a at (0,0,0), both In and R in site 4b at (0,0,1/2) according to their proportion in the samples and Te in site 8d at (x,1/4,1/8), x being close to 0.2220. When doping the same rare earth element, as the increase of x in CuIn1-xRxTe2 (x=0-0.2), the gain size and cell volume increase. However, there is no big difference between x=0.2 and x=0.3, illustrating the CIRT compounds are limited solid solubility and the maximum solid solubility is at about x=0.2.When doped the same amount of rare earth elements, with the increase of the atomic weight of rare earth elements in compounds, lattice constants decrease. Hence rare earth doped CuInTe2 compounds are promising semiconductor materials for solar cells. |
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