Photoelectric Properties And Theoretical Design Of Highly Efficient Porphyrin Dye Sensitizers

Dye-sensitized solar cells?DSSCS? have been regarded as next-generation photovoltaics, which have attracted a wide attention of many research scholars because of easy fabrication, low cost,and more versatility. Studies have shown that dye sensitizers have important effect on photoelectric conversion efficiency?PCE?. So far, Dye-sensitized solar cells with 13% efficiency achieved through the molecular engineering of porphyrin sensitizers. But the light absorption range of porphyrin dye sensitizer is still limited to the UV-vis region. Therefore, in order to further improve the PCE of DSSCS, broadening the absorption range and increasing the absorption intensity of porphyrin dye sensitizeris are very necessary.Considering the adjustment of the free-base-porphyrin on the electronic structure and the related properties. Therefore, in order to further investigate the role of porphyrin–free-base in the modification of electronic structures and related properties, the novel porphyrin dyes named DTBCMP and DTBC-TP were designed by varying the porphyrin–free-base units in the ? conjugation of DTBC. The result indicates that, the extension of conjugate bridge with porphyrin–free-base units results into the elevation of the highest occupied molecular orbital?MO? energies, the decrease of the lowest unoccupied MO?LUMO? energies, the reduction of HOMO-LUMO gap, the red-shift of absorption bands, and the enhancement of absorbance. The free energy change demonstrates that the introducing more porphyrin–free-base in conjugate bridge induces the faster rate of electron injection.The transition properties and MO characters suggest that the different transition properties might lead to different electron injection mechanism. In terms of electronic structure, absorption spectra,light harvesting efficiency, and free energy changes, the designed DTBC-TP would be a promising candidate dye sensitizer of DSSCs.Here, by comparative study on the electronic structure and the related features of excited state of the porphyrin dye sensitizers SM315, SM371 and YD2-o-C8. The geometric structure parameters show that insert BTD groups, extending the conjugate bridge length. State density data shows that SM371 donors introduced more electrons than YD2-o-C8 donor, BTD act as accept group. Light absorption properties indicate that insert BTD groups to broaden the range of light absorption.Charge transfer data suggests that the BTD effectively improve the excited charge transfer of dye sensitizers. Electron injection and dye regeneration of free energy change suggest that SM315,SM371, YD2-o-C8 has enough electron injection and regeneration rate.Toward Panchromatic Organic Functional Molecules H₂?TAnP? and H₂?TAzP? have been reported, the absorption performance of H₂?TAnP? and H₂?TAzP? are affected by substituent group in different position, thus in this paper, we designed a series of D-?-A structure dyes, using H₂?TAnP? and H₂?TAzP? as ? bridge and the other parts are the same as YD2-o-C8. DFT andTDDFT are used to calculate the electronic structure and optical properties. The calculated results indicated, H₂?TAnP? and H₂?TAz P? were designed to the D-?-A structure, reduced HOMO-LUMO gap and red-shifted absorption spectrum, besides, with the better free energy change for electron injection and regeneration. All in all, the designed dyes, especially H₂?TAnP?-? and H₂?TAzP?-?used in dye sensitized solar cell, maybe will further breakthrough dye-sensitised solar cells efficiency record.