Abstract
In this paper, the synthesis and characterization of CuIn1−xGaxSe2 (0 ≤ x ≤ 1) nanocrystals are reported with the influences of x value on the structural, morphological, and optical properties of the nanocrystals. The X-ray diffraction (XRD) results showed that the nanocrystals were of chalcopyrite structure with particle size in the range of 11.5–17.4 nm. Their lattice constants decreased with increasing Ga content. Thus, the x value of the CuIn1−xGaxSe2 nanocrystals was estimated by Vegard’s law. Transmission electron microscopy (TEM) analysis revealed that the average particle size of the nanocrystals agreed with the results of XRD. Well-defined lattice fringes were shown in the TEM images. An analysis of the absorption spectra indicated that the band gap energy of these CuIn1−xGaxSe2 nanocrystals was tuned from 1.11 to 1.72 eV by varying the x value from 0 to 1. The Raman spectra indicated that the A1 optical vibrational mode of the nanocrystals gradually shifted to higher wavenumber with increasing x value. A simple theoretical equation for the A1 mode frequency was proposed. The plot of this equation showed the same trend as the experimental data.
Highlights
In recent years, due to issues of global warming, the exhaustion of traditional and nonrenewable energy sources, and the goal of gradually reducing nuclear power generation, the demand for clean, safe, and renewable energy around the world has increased significantly
We report the synthesis of CuIn1−xGaxSe2 nanocrystals over the entire nominal composition range (0 ≤ x ≤ 1) by a solution-based method [26]
Compared with the standards of the International Centre for Diffraction Data (ICDD) for CuInSe2 (JCPDS 01-087-2265) and CuGaSe2 (JCPDS 01-075-0104), it can be confirmed that all nanocrystals exhibited tetragonal structures with space groups of I-42d, i.e., chalcopyrite structures
Summary
Due to issues of global warming, the exhaustion of traditional and nonrenewable energy sources, and the goal of gradually reducing nuclear power generation, the demand for clean, safe, and renewable energy around the world has increased significantly. The research and development of photovoltaic devices have attracted great interest and attention. The earliest photovoltaic devices were made of crystalline silicon, which is currently the main material for the mass production of solar cell modules. Due to high production costs, many researchers have turned to other photovoltaic materials in order to replace crystalline silicon. CuIn1−xGaxSe2 has good optical properties, such as intrinsic high optical absorption coefficient (α ≈ 105/cm), wide absorption range, good radiation stability [2,3,4,5], and a direct bandgap which is adjustable by changing the composition ratio of In to Ga. CuIn1−xGaxSe2 has good optical properties, such as intrinsic high optical absorption coefficient (α ≈ 105/cm), wide absorption range, good radiation stability [2,3,4,5], and a direct bandgap which is adjustable by changing the composition ratio of In to Ga For this reason, it is regarded as an excellent absorber layer material for thin-film solar cell applications [6,7]. CuIn1−xGaxSe2 could be a promising material for other optoelectronic applications because its composition tunability opens another parameter with which to achieve specific properties and performance [9]
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