The absorption properties of p-type TlInxGa(1-cursive greek chi)Se2 and TlGaSe2

p - TlGaSe2, p - TlIn0.3Ga0.7Se2 and p - TlIn0.5Ga0.5Se2 single crystals were grown by the modified Bridgman-Stockbarger method in our crystal growth laboratory. The absorption measurements were carried out on p - TlIncursive Greek chiGa(1-cursive Greek chi)Se2 samples in temperature range 10-300 K in steps of 10 K. The binding energies of p - TlGaSe2, p - TlIn0.3Ga0.7Se2 and p - TlIn0.5Ga0.5 Se2 were obtained as 35.0 meV, 16.5 meV and 14.5 meV, respectively. THe direct band gaps were calculated as 2.244 eV, 2.195 eV, 2.164 eV in p - TlGaSe2, 2.158 eV, 2.131 eV, 2.098 eV in p - TlIn0.3Ga0.7Se2, and 2.107 eV, 2.075 eV, 2.019 eV in p - TlIn0.5Ga0.5Se2 respectively, at sample temperatures of 10 K, 140 K and 300 K. The indirect band gaps were calculated as 2.196 eV, 2.127 eV, 2.073 eV in p - TlGaSe2 2.130 eV, 2.101 eV, 2.064 eV in p - TlIn0.3Ga0.7Se2 and 2.090 eV, 2.054 eV, 2.004 eV in p - TlIn0.5Ga0.5Se2 respectively, at 10 K, 140 K and 300 K. There is an abrupt change in the energy peak for p - TlGaSe2 in the temperature range 135-150 K. The values that we obtained from the energy peak change may be at a phase transition temperature.