Theoretical studies on the absorption spectra and intramolecular charge transfer of push-pull zinc porphyrin dyes for dye-sensitized solar cells

The electronic structures, absorption spectra and intramolecular charge transfer properties of five push-pull zinc porphyrin analogs with different donor group and π bridge have been investigated by density functional theory(DFT) and TD(time-dependent)-DFT approach. The results show that the asymmetrical substituted diphenylamine group is favorable to the Q-band absorption of porphyrin dyes. The absence of the acetylenic bond in the π bridge part leads to the result that the B-band and the Q-band are blue-shifted and their absorption strength become weaker compared with that containing acetylenic bond, respectively. The introduction of the benzothiadiazole into the π bridge improves the intramolecular charge transfer.