Synthesis Of Sensitizers Based On Carbazole And Bidithiophene Derivatives And Investigation On Their Conjugation And Photoelectric Properties

Dye-sensitized solar cells(DSSCs),as one of the branches of solar cells,have been the focus of research because of their extremely broad application prospects.Pure organic dyes are favored by researchers because of their cheap raw materials,diversified designs,simple synthesis steps and long-term stability.The photophysical and electrochemical performance tests were carried out by means of ultraviolet-visible absorption spectrum and fluorescence emission spectrum test,cyclic voltammetry test,J-V curve,monochromatic light conversion efficiency(IPCE)and electrochemical impedance(EIS)test.Meanwhile,the density functional theory is used to calculate the electronic energy level distribution and the molecular optimal configuration.The specific work content is as follows:In the first chapter,the working principle of dye-sensitized solar cells is reviewed and several types of typical sensitizers are introduced.Through observation of DSSCs devices with high efficiency sensitizers,designers have been looking for dyes that can have a broad spectral response while effectively inhibiting intermolecular aggregation.To satisfy both,the degree of conjugation of the entire dye molecule must be carefully considered.In previous molecular designs,the main focus of donors was on the introduction of anti-aggregation groups,while neglecting the study of the flatness of the donor;Although the flatness of the connecting bridge has been repeated many times in single anchor dyes,there is very little research on double anchoring dyes.Based on the above discussion,the research content of this paper is proposed.In the second chapter,we mainly study the effect of the series of donor changes on molecular conjugation.Four D-A-π-A metal free sensitizers,QL1-4 with N-phenyl carbazole derivatives as donors were specifically designed and synthesized for the first time,where thiophene was used as a ?-bridge,and quinoxaline as auxiliary electron-withdrawing π-spacers.A series of carbazole-based donors were synthesized by carbazole ring expansion method.The effect of donor planarity on dye structure and battery performance was researched.5-phenyliminostilbene(ISB)exhibits stronger electron donor capabilities than other donors,whose ?-bridge has the most suitable flatness,which is more conducive to intramolecular electron transfer.QL3 finally achieved the highest high efficiencies of 6.22%.What’s more,when QL3 was co-sensitized with WL5,the photovoltaic properties are further improved achieving a power conversion efficiency of 8.26%,which is much higher than 7.75% for N719 at the same conditions.Through the study of donors,it has been proved that the ring-expanding method can affect the donor’s electron donor ability and the planarity of the entire dye molecule.In addition,the introduction of sterically hindered groups on the donor should be controlled to a suitable size to reduce the impact on the reduction of dye adsorption.In chapter three,we mainly study the influence of the degree of conjugation of the connecting bridge on the structure of the double anchored dye and the relationship between structure and performance.And three novel phenothiazine based A–D–π–D–A type double anchoring dyes TPTZ1-3 are synthesized,where main variations are performed on the linkage ways of dithiophene(DT).The relationship between the photovoltaic properties and the different connection bridge of these organic dyes are studied systematically.It is found that a strategical variation on the linkage ways of dithiophene(DT)can obviously affect the twisted degree of backbone and have a great effect on inhibiting the intermolecular aggregation.Compared with a bulky rigid group substituted on TPTZ3,introducing flexible side chains at suitable site on the TPTZ1-2 seems to be a more effective strategy to achieve higher photoelectric performance for double anchoring dye.Finally,the DSSCs based on TPTZ2 exhibits high efficiency of 7.50%,reaching 99% of N719-based standard cell at the same condition.The results provide a new approach for highly efficient anti-aggregation organic sensitizers.