Synthesis And Photovoltaic Performance Of Truxene-based Asymmetric Arylamine Dyes

Dye-sensitized solar cells (DSCs) have recently received great attention because of theirease of fabrication and cost-effectiveness compared with silicon (Si) based photovoltaicdevices. During the past two decades, numerous research attempts have been made toexploring new photosensitizers to assist in the development of dye-sensitized solar cells(DSCs). Of all the photosensitizers examined thus far, the arylamine organic dyes, holding therecord for validated efficiency of over10.3%, are promising candidates for highly efficientDSCs.Triarylamine photosensitizers have the following advantages: high molar absorptioncoefficient; effectively suppress electron recombination; prevent aggregation. According toabove reasons of this issue, we design and syhthesis three new organic photosensitives. Theyare three truxene-based modified asymmetric triarylamine as electron donor, cyano acetic acidas an electron acceptor,3,4-ethylenedioxythiophene (EDOT) as conjugated bridge to formD-π-A type dye(M20, M21and M22). Emphasis on the study of the influence of thephotosensitizers’ structure to the photovoltaic performance.Part of the molecular structure of M20is introduced to broaden the EDOT π conjugatedsystem of the power supply portion; M21and M22, respectively, due to the introduction of4-methoxybiphenyl and dipropylfluorene reduce the bandgap between highest occupiedmolecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO). Therefore, thethree dyes intramolecular charge-transfer transition (ICT) absorption peak wavelength (520nm,519nm and524nm) compared to the M4(506nm) are red-shifted14nm,13nm and18nm.Value of three dyes HOMO energy level values than [Co(phen)3]2+/3+and I—/I—3oxidation-reduction potential (0.62V and0.4V vs NHE) to be more positive, indicating thatthere is sufficient driving force reduce dye regeneration of Co2+and iodine ions ruduction.LUMO energy level values of the three dyes (i.e. excited state oxidation-reduction potentialof the dyes, respectively-1.22V,-1.11V and-1.11V vs NHE) than the conduction bandenergy levels of TiO2(ECB,-0.5V vs NHE) is more negative, indicating that the dye canprovide sufficient driving force for the electron injecting electrons into the excited state TiO2band. Three dyes are in line with the level matching principle of DSCs.Effect of TBP content of cobalt in the electrolyte on the battery performance can bestudied. Found at a concentration of0.8M TBP cobalt electrolyte optimal performance me.The study also found that M21and M22dye introduction of a strong electron donor unit (4-methoxybiphenyl and dipropylfluorene) can significantly improve the ability of capturinglight, short-circuit photocurrent density and the photoelectric conversion efficiency of the cell.Taking all the factors measured three newly synthesized dyes M22optimal performance, thePCE of M22up to7.89%PCE.