Investigation Of Fused Ring Photosensitizers In Dye-Sensitized Solar Cells

The main function of photosensitizers are to absorb photons and convert them into electrons in dye-sensitized solar cells(DSSCs),which is one of the main factors affecting the photo-conversion efficiencies of solar cells.Therefore,the development of new photosensitizers play a crucial role in improving the efficiency of solar cells.The different fused ring dye donors are developed and designed to adjust the dye energy level and broaden the spectral response.The different electrolytes are used to improve the photovoltaic performance.The dithiophene dipyrrole(DTP)core as a strongly electron donor is applied by introducing different numbers of alkoxy chains to modify DTP,which obtain the more negative HOMO energy level and broader light responses of AJ101 and AJ102.Compared with AJ102,the donor of AJ101 with an additional alkoxy group reduced intermolecular aggregation and thus electron recombination.A larger dihedral angle between the donor and the ? bridge reduced the planarity of the molecule,which DSSC devices with I-/I3-as electrolyte obtained photo-conversion efficiency(PCE)of 8.0%and Voc of 784 mV.The donor of thiophene of AJ102 as the connecting point with ? bridge to reduce the intermolecular torsion and expand the spectral response,which DSSC device obtained a higher photocurrent(Jsc)of 20.0 mA/cm2 and a higher PCE of 9.5%.A series of photosensitizers AJ201,AJ202 and AJ206 are synthesized by using low-cost carbazole as a raw material.The FeCl3 oxidation forms a donor with high conjugated fused ring polycarbazole,which has moderate electron donor capacity and adjusted the HOMO level of the photosensitizers by acetenyl.These photosensitizers satisfy the high HOMO level of the new Cu?/?(tmby)2(TFSI)1/2 electrolyte with sufficient driving force for dye regeneration.Through comparison,it is found that the dye AJ206 with acetenyl inserted into the anchoring group reduced the charge recombination ratio,broader spectral response and faster electron injection,which DSSC device obtained PCE of 10.8%and Voc of 1002 mV.Thiophene is introduced to carbazole to form a fuse ring as the donor to synthesize the dye AJ303 by FeCl3 oxidation,and the non-cyclic dye AJ301.AJ303 bases on Co(bpy)33+/2+and Cu?/?(tmby)22+/+electrolyte,which DSSC devices obtained the PCE of 10.3%and 8.2%,respectively.The high conjugate ring dye AJ303 has smaller molecular structure,higher IPCE response and lower charge recombination rate.Therefore,it is an promising approach expand the structure of conjugate ring by fusion to improve the dye conversion efficiency.The introduction of alkyl benzyl modified carbazole as the fused donor is synthesised and the strong electron-deficient group of pyrrole pyrrolidone as ? bridge used to obtain dye AJ502.TZ101 and TZ102 were synthsized with indolo[3,2-b]carbazole as donor and the electron-deficient group of 5,6-difluoro-benzo[d][1,2,3]triazole and benzo[d][1,2,3]triazole as? bridge,which TZ101 contains two F atoms on bridge and TZ102 not it.The PCEs are greatly improved by mutual co-sensitization with AJ502 and TZ101 to obtain Voc of 1060 mV and PCE of 10.3%,a value almost is equal to the sum PCEs of DSSC device sensitized by the single dye of AJ502 and TZ101.It was found that the co-sensitization of two different photosensitizers on TiO2 via inter-molecular reaction is an efficient way to expand the light capture range for DSSCs.