Solvothermal Preparation and Spectroscopic Characterization of Copper Indium Diselenide Nanorods

Single-crystalline chalcopyrite CuInSe2 nanorods (CuInSe2NRs) of 50-100 nm in diameter and up to a few micrometers in length have been synthesized solvothermally. High-resolution transmission electron microscopic
images of the CuInSe2NRs reveal the d-spacing of 0.335 nm for the (112) crystalline planes and a growth direction along [331]. The near-infrared absorption spectrum of the chalcopyrite CuInSe2NRs shows a peak
maximum at 1162 nm and an onset at 1262 nm, indicating no apparent blue-shift compared with those of Cu-rich CuInSe2 thin films. An intense peak at 175.1 cm-1 in the room-temperature Raman scattering spectrum
of CuInSe2NRs corresponds to the A1 phonon mode of tetragonal CuInSe2 chalcopyrite. The narrower full width at half-maximum (fwhm) of 9.5 cm-1 for CuInSe2NRs, in comparison with fwhm ∼ 12 cm-1 for CuInSe2 films, indicates a uniform size distribution and single crystallization in the nanorods. Analysis of the photoluminescence from the single-crystalline CuInSe2NRs measured at 10 K has categorized the emission into seven groups of transitions as characterized by free excitons, bound excitons, conduction band to acceptor levels, and bound excitons at different defects.