The　molecular　structures　and　absorption　spectra　of　triphenylamine　dyes　containing　variable　thiophene　units　as　the　spacers　(TPA1-TPA3)　were　investigated　by　density　functional　theory　(DFT)　and　time-dependent　OFT.　The　calculated　results　indicate　that　the　strong　conjugation　is　formed　in　the　dyes　and　the　length　of　conjugate　bridge　increases　gradually　with　the　increased　thiophene　spacers.　The　interfacial　charge　transfer　between　the　TiO2　electrode　and　TPA1-TPA3　are　electron　injection　processes　from　the　excited　dyes　to　the　semiconductor　conduction　band.　The　simulated　absorption　bands　are　assigned　to　pi　-＞pi*　transitions,　which　exhibit　appreciable　red-shift　with　respect　to　the　experimental　bands　due　to　the　lack　of　direct　solute-solvent　interaction　and　the　inherent　approximations　in　TD-DFT.　The　effect　of　thiophene　spacers　on　the　molecular　structures,　absorption　spectra　and　photovoltaic　performance　were　comparatively　discussed　and　points　out　that　the　choice　of　appropriate　conjugate　bridge　is　very　important　for　the　design　of　new　dyes　with　improved　performance.　(C)　2010　Elsevier　B.V.　All　rights　reserved.