Temperature dependence of the fundamental absorption edge in CuIn3Se5

From the study of the temperature dependence of the optical absorption spectra, the energy gap $E_G$ of ${\mathrm{CuIn}}_{\mathrm{3}}{\mathrm{Se}}_{\mathrm{5}}$ between 10 and 300 K are calculated using the model proposed by Elliot. This variation is compared to the semiempirical relation suggested by Manoogian–Woolley. The Debye temperature ${\Theta }_D,$ the dielectric constant ${\epsilon }_0,$ and the effective masses of free excitons $m_{\mathrm{ex}},$ electrons $m_e,$ and holes $m_h$ are estimated from the analysis of the adjustable parameters of these models.