Reorganization energy is one of the important factors to decide the rate of electron transfer according to the Marcus theory. Small reorganization energy is highly desirable in design of optoelectronic and electronic devices like as organic light emitting diode. For this reason, reorganization energy of aromatic diamine derivatives, N,N′-diphenyl-N,N′-bis(3-methylphenyl)- (1,1′-biphenyl)-4,4′-diamine (TPD) and 4,4′-diphenyl-N,N,N′,N′-tetraphenylbenzidine (DTPB) have been studied theoretically by self-exchange electron transfer theory. By executing the Gaussian 03 calculation we can easily figure out the optimization point which needed for calculation of the inner reorganization energy (λ) of self-exchange electron transfer reaction. Also ionization potential and electron affinities of these molecules can be calculated at the density functional theory level with basis set 6-31G** and 6-31G* using Gaussian 03 software on the basis of ab initio method. It gives possibility to develop a semi-empirical model for the observed absorption and photoluminescence spectrum.