Photoluminescence of CuInS2 single crystals grown by both the traveling heater method (THM) and chemical vapor transport (CVT) has been investigated at 4.2, 78, and 300 K. Intense emission in the near-band-edge region caused by free and bound excitons has been detected for both types of crystals. Taking into account the energy position of the luminescence line of the ground (n = 1) and first excited (n = 2) states, the binding energy for free A excitons has been estimated to be about 19.7 and 18.5 meV for CuInS2 grown by CVT and THM, respectively.
Mudryi, A. V., Karotki, A. V., Yakushev, M. V., & Martin, R. W. (2009). Photoluminescence of CuInS2 single crystals grown by traveling heater and chemical vapor transport methods. Journal of Applied Spectroscopy, 76(2), 215-219. https://doi.org/10.1007/s10812-009-9163-5