Tris(8-hydroxyquinoline) gallium (Gaq3) is an alternative compound to tris(8-hydroxyquinoline) aluminum (Alq3) which is an organic light emitting diode (OLED) material. The performance of Gaq3 incorporated into OLEDs has been seen to be superior compared to that of Alq3-based ones but the OLED properties of a substituted Gaq3 complex has been not studied yet. For this reason, the OLED performances of Gaq3 and its derivatives were investigated theoretically. Gaq3, functionalized Gaq3 derivatives and their dimers were designed. While monomer calculations were performed on the B3LYP/6-31G(d) level, dimer computations were carried out on the B3LYP/TZP level. The reorganization energies (lambda e and lambda h), ionization potentials and electron affinities (adiabatic and vertical), energy gaps, effective transfer integrals (Je and Jh) and charge transfer rates (Ke and Kh) of the aforementioned molecules were calculated. Based on these parameters, the OLED behaviors of the compounds were estimated.