The band structure of CuInTe2 studied by optical reflectivity

Abstract

CuInTe2 is a semiconductor with high potential for use as a thermoelectric material and as the absorber in thin film solar cells. Studying the optical reflectivity spectra of CuInTe2 single crystals resolves resonances at 1.054 eV and 1.072 eV, which are assigned to the A and B free excitons. Photoluminescence spectra exhibited a peak due to the A free exciton at 1.046 eV. Varshni coefficients were found for both excitons. Zero temperature bandgaps EgA = 1.060 eV and EgB = 1.078 eV were determined for the A and B valence sub-bands, respectively. The splitting due to crystal-field ΔCF and spin-orbit effects ΔSO were calculated as -26.3 meV and 610 meV, respectively, using the determined EgA and EgB and a literature value of EgC.

Synergistic Regulation of Phonon and Electronic Properties to Improve the Thermoelectric Performance of Chalcogenide CuIn1−xGaxTe2:yInTe (x = 0–0.3) with In Situ Formed Nanoscale Phase InTe

“…Ternary CuInTe 2 compound with a chalcopyrite structure has recently received much attention in thermoelectrics in a sense that it has a high Seebeck coefficient (≈400 μ VK −1 ) and optimal carrier concentration n (10 18 –10 19 cm 3 ) at room temperature (RT) . Besides, its direct bandgap (≈1.05 eV) is much larger than those of traditional TE materials, for example, 0.11 eV for Bi 2 Te 3 , 0.14 eV for Sb 2 Te 3 , and 0.18 eV for PbTe, which prevent the degradation of the thermoelectric performance from the thermally activated minority carriers at high temperatures . However, this compound gives a relatively high thermal conductivity with the κ L value of 4.0–7.0 W m −1 K −1 at RT and 1.0–1.3 W m −1 K −1 at ≈850 K, therefore, the TE performance of the pristine CuInTe 2 is still low, evidenced by many experiments with the ZT value being only 0.24–0.76 …”

“…∆ CF splitting and spin-orbit ∆ SO effect, [4] the crystal structure engineering, which is successfully employed in the Ag(Zn)introduced CuInTe 2 compound systems, [29,30] may be an alternative way to reduce the lattice κ L . Unfortunately, the power factors do not increase significantly.…”

A Magneto‐Reflectivity Study of CuInTe2 Single Crystals

“…Optical reflectance (OR) spectra of CuInTe 2 , measured at zero magnetic field and 4.2 K, exhibit two excitonic oscillations earlier assigned to the A and B free excitons at 1.053 and 1.072 eV, respectively. [17] These excitons are shown in Figure 1a.…”

“…Single crystals of CuInTe 2 were grown using the vertical Bridgman technique. [17,26] Crystals from the middle part of the ingot were cleaved and then examined at zero magnetic fields for the presence of excitons in the PL and OR spectra. Such spectra, measured at liquid helium temperatures, were reported earlier.…”

“…Such spectra, measured at liquid helium temperatures, were reported earlier. [17] The elemental composition of the samples was measured by wave-length dispersive spectrometry as Cu Another fiber was used to collect the MR signal and deliver it to the slits of a 0.5 m focal length single-grating (1800 grooves mm À1 ) spectrometer with a liquid nitrogen-cooled InGaAs array detector. The MR spectra were measured at a spectral resolution of 0.2 meV.…”