Synthesis And Performance Study Of Thiourea Triphenylamine Dyes Based On Thienopyrrole Dione Bridge Chain

In order to deal with the serious energy crisis,the development and utilization of new energy have become a major tendency.Solar energy has drawn an intensive interesting due to its clean and renewable.In the field of solar photoelectric conversion,dye-sensitized solar cells(DSSCs)have great potential for application because of their low cost,simple preparation process,and low environmental pollution.As a key component of DSSCs,the dye sensitizers play an important role in absorbing sunlight and injecting electrons.Their performance determines directly the photoelectric conversion efficiency of DSSCs.Our group has reported cycle thiourea triphenylamine organic dyes previously,which has a strong electron-donating ability and a wide spectral absorption range.In this paper,novel D-A-?-A type organic dyes with the cycle thiourea triphenylamine as a donor were designed and synthesized,which incorporated in thieno[3,4-c]pyrrole-4,6-dione(TPD)as auxiliary acceptor and double-acceptor dyes with TPD as the core part and two anchor groups were designed.Their photophysical absorption,electrochemical measurement and photovoltaic performance were investigated and calculated with their structure by DFT.The main contents are as follows:1.Dye sensitizers with D-A-?-A molecular structure and two anchor groups were synthesized from TPD via a series of classic reactions,involving NBS bromination,Suzuki coupling,Vislmier-Haack formylation,Heck coupling and Knoevenagel condensation reactions.The structures of the target compounds and interrmediates were confirmed by NMR,IR,and MS.2.The photophysical properties of the dyes was tested and the influence of the TPD electron-withdrawing groups was examined.UV-vis spectra showed that compared with AZ6,the absorption peaks of ST dyes undergo red-shift and the spectral absorption maximum range is broadened,due to the better planarity.Among three dyes,extending the length of ?-linker,ST3 has the largest degree of red-shift,and the absorption wavelength was 472 nm.Moreover,compared with single-acceptor dyes,double-acceptor dyes have a larger red-shift,wider spectrum absorption range and a higher molar extinction coefficient.3.Electrochemical measurement showed that the HOMO/LUMO energy levels of ST dyes and double-acceptor dyes meet the energy level requirements of DSSCs.Impedance performance found that the ST dyes have obvious electronic recombination and shorter electron lifetime.4.The optimized configuration and HOMO/LUMO orbitals as well as the electron distribution of dyes are calculated by DFT.The introduction of TPD reduces the energy bandgap and facilitates the excitation of the dyes.The HOMO orbital of the double-acceptor dye is less distributed on the TPD,indicating that the TPD segment has poor electron-donating ability.5.Photovoltaic performance of the cells shows that the IPCE and PCE of the ST dyes are lower than reference dye of AZ6.The main reason is that the ?-? stacking or aggregation of the ST dyes are observed,resulting in serious electron recombination.Among them,ST2 exhibited the highest photoelectric conversion efficiency(?=3.23%),due to the furan linker with large torsion angle,which inhibited the dye aggregation.When ST2 co-sensitized with 8 mM CDCA,the PCE was increased from 3.23%to 3.93%.The low PCEs of the double-acceptor dyes were obtained,due to the poor electron-donating ability of TPD as a donor.