A systematic theoretical method on the investigation of the process of light-emitting in organic conjugated molecules,metal complexes with organic ligands,polymers,and oligomers has been proposed.The hole-and electron-injection/transport,exciton binding energy and absorption and emission spectra of these materials have been studied.To find new multifunctional OLED materials,a number of high-performanced light-emitting complexes were designed.In addition,it is easy to tune the emission wavelengths and hole-and electron-injection/transport by altering the molecular structures.As a result,this work should be useful for developing new and high-powered π-conjugated materials for OLEDs.