Abstract
The chalcopyrite Cu(In,Ga)Se2 (CIGS) alloy system has received strong interest in recent years because of its potential for the development of high efficiency and low cost solar cells. The bandgap energy can be varied between 0.9 and 1.68 eV by composition ratio of In and Ga and the absorption coefficient is very high of abobe 105 cm-1. In our previous work1, I-III-VI2 chalcopyrite compound Cu(In0.2, Ga0.8)Se2 (CIGS) single crystal was successfully grown by traveling heater method (THM). The powder X-ray diffraction (XRD) pattern showed preferred orientations of (112), (220) and (312) planes, confirming the chalcopyrite structure. In Raman spectra, the A1 mode peaks expected for CIGS were observed, and no secondary phases were observed. The full-width at half-maximum (FWHM) of the X-ray rocking curve (XRC) for the (112) oriented CIGS single crystal is 103 arcsec. The good-quality single-phase CIGS single crystal can be obtained1). In this work, Ga-rich composition ratio CIGS single crystals could be also successfully grown by THM. At the ratio of Ga / (Ga + In) > 0.3, the CIGS changed from n-type conduction to p-type conduction. It was assumed that Se vacancies are reduced with increasing Ga ratio from the results of Energy dispersive X-ray spectroscopy. 1)Nagaoka, et al., Renewable Energy 2015, 79, 127-130.
Published Version
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