Temperature dependence of the fundamental absorption edge in CuGaSe2

The temperature dependence of the fundamental absorption edge in CuGaSe₂ single crystals was determined in the temperature range from 15 to 300 K. Above about 120 K the gap energy changes linearly with temperature with dE_g/dT = ? (2.1 ± 0.1) eV K^?1. The downshift in dE_g/dT of the I–III–VI₂ compounds compared to their II–VI analogs is discussed accounting for the p-d hybridization of the uppermost valence band.