Density　functional　theory　(DFT)　and　time-dependent　DFT　(TD-DFT)　calculations　have　been　employed　to　investigate　the　molecular　structures　and　absorption　spectra　of　two　dyes　containing　diphenylaniline　and　4-diphenylamino-diphenylaniline　as　donor　moiety　(TPA1　and　TPA3).　The　geometries　indicate　that　the　strong　conjugation　is　formed　in　the　dyes.　The　electronic　structures　suggest　that　the　intramolecular　charge　transfer　from　the　donor　to　the　acceptor　occurs,　and　the　electron-donating　capability　of　4-diphenylamino-diphenylaniline　is　stronger　than　that　of　diphenylaniline.　The　computed　highest　occupied　molecular　orbital　(HOMO)　energy　levels　are　-5.31　and　-4.90　eV,　while　the　lowest　unoccupied　molecular　orbital　(LUMO)　energies　are　-2.29　and　-2.26　eV　for　TPA1　and　TPA3,　respectively,　revealing　that　the　interfacial　charge　transfer　between　the　dyes　and　the　semiconductor　electrode　are　electron　injection　processes　from　the　photon-excited　dyes　to　the　semiconductor　conduction　band.　Furthermore,　all　the　experimental　absorption　bands　of　TPA1　and　TPA3　have　been　assigned　according　to　the　TDDFT　calculations.