Abstract
Principal optical properties of Tl1-xIn1-xSixSe2 solid state crystalline alloys were studied. The influence of the x on the principal optical and structural features was explored. Temperature features of the band energy gap are studied. The possible explanation of the observed behavior is given within a framework of the Urbach rule approach. The role of intrinsic defective sub-system and anharmonic electron-phonon interaction is discussed. A possible application of the titled materials for the infrared optoelectronic is discussed. The replacement of In atoms by Sn is evaluated. Additionally studies of influence of x on the optoelectronic features is done. The formation of the positive charged ions (donors) and negatively charged ions is explored within the introduced intrinsic defect models.