The study of the process of electric charge carrier thermalization in molecular semiconductors is presented. For the strong interaction of the photogeneration center with its neighbors the direction of the initial velocity of the charge carrier is independent on the incident light parameters. In the case of weak interaction the initial velocity of the charge carrier is almost perpendicular to the direction of light propagation. The thermalization process is described by Langivin equations. The strength of the photogeneration center interaction with neighbors determines the thermalization length dependence on the ambient temperature and the frequency of the incident light beam. Comparisons with experimental results are presented.