Temperature Dependences of Optical Energy Gaps of SbSI@CNT and SbSeI@CNT

This paper presents for the first time temperature dependences of optical energy gaps of SbSI@CNT and SbSeI@CNT, i.e. carbon nanotubes (CNTs) filled with antimony sulfoiodide (SbSI) and antimony selenoiodide (SbSeI). The heterostructures were prepared sonochemically using CNTs and elemental Sb, S or Se and I in the presence of solvent under ultrasonic irradiation. Spectral characteristics of diffusive transmittance and reflectance of SbSI@CNT and SbSeI@CNT were measured in temperature range 274 K < T < 333 K. The determinal temperature dependence of indirect forbidden optical energy gap of SbSI@CNT has been fitted with $E_\text{gIf} (T) = (1.92(2)-3.6(6) \times 10^{-4} \times T) eV$. Indirect allowed optical energy gap of SbSeI@CNT has been fitted with $E_\text{gIa} (T) = (1.817(5)-7.1(2) \times 10^{-4} × T) eV$.