Study On The Synthesis And Optoelectronic Properties Of Diindolothiazine Conjugated Molecules

Organic optoelectronic materials are widely applied to electronic components and play an important role in electronic industry production.Compared to inorganic optoelectronic materials,organic optoelectronic materials have more advantages.For example,organic optoelectronic materials have low cost,diverse and adjustable structure,lightweight and flexible characteristics,which indicates that organic optoelectronic materials in the field of photoelectric conversion and electroluminescence have bright development prospects.In recent years,many organic conjugated materials with novel configurations have been designed and synthesized for use in dye-sensitized solar cells（DSSCs）and organic electroluminescent diodes（OLEDs）with good results,both of which have been commercialized to some extent.Phenothiazine has unique advantages:（i）the electron-rich sulfur and nitrogen heteroatom render phenothiazine a stronger donor than other amines;（ii）the no-planer butterfly conformation helps to inhibit the quenching of molecular aggregates.This indicated the suitability of phenothiazine as a donor for application in organic conjugated materials;while carbazole has good electron transport properties,it is also suitable as an organic conjugate unit for the construction of organic optoelectronic materials.In this study,phenothiazine and carbazole are combined in the form of a shared benzene phase-conjugate ring to be the first synthesize diindolothiazine.Bilateral symmetrical ring incorporation at the 3 and 4 positions,6and 7 positions of phenothiazine has been achieved to construct new large conjugated aromatic ring structures relating to phenothiazine derivatives.What’s more,the diindolothiazine was applied to the construction of dye sensitizers and organic light-emitting materials,which studied the photovoltaic properties of diindolothiazine dye sensitizers in DSSCs and the electroluminescent properties of diindolothiazine light-emitting materials in OLEDs.The specific research work is mainly based on the following parts:In Chapter 2,the D（-π-A）₂ type dye sensitizers WX1 and WX2 were designed based on diindolothiazine as the donor,thiophene or hexylthiophene as theπ-bridge,and cyanoacrylic acid as the acceptor.The photophysical properties,electrochemical properties and photovoltaic properties of these two dye sensitizers in DSSCs are studied.It has been demonstrated the dyes WX1 and WX2 all show high molar extinction coefficients.Especially dye WX1 has high molar extinction coefficients up to 64100 M^-1 cm^-1 and maximum PCE up to 5.97%.The results indicate that diindolothiazine is an efficient dye donor.However,hexylthiophene as aπ-bridge for WX2,the distorted molecular skeleton,and excessive bulk potential resistance reduce the loading of WX2 on the surface of the Ti O₂ film.This affects the light-harvesting capacity of the DSSCs,leading to a sharp drop in photocurrent and a significantly lower PCE value than WX1.This indicates that the large bulk potential resistance of the dye and the distorted molecular skeleton are not conducive to the light-harvesting process.In addition,to further enhance the photovoltaic performance of the DSSCs,we use the WL8,a dye with a complementary absorption spectrum and molecular volume size matching that of WX2,to conduct the co-sensitization experiments.Consequently,the PCE value of WX2+WL8 up to6.69%,both higher than the photoconversion efficiency of a DSSCs consisting of individual dye molecules of WX2 or WL8.In Chapter 3,based on the serious problem of device efficiency roll-off in OLEDs,the ring amplification of phenothiazine,which has stable cationic radical properties,was designed to synthesize diindolothiazine.Followed by derivatization of diindolothiazine in the form of WX-G modified by long alkyl chains and WX-GB modified by short alkyl chains.Furthermore,the nucleus of diindolothiazine was also adjusted to dithienopyrrole to design the synthesis of diindolodithienopyrrole（WX-B）.In addition,WX-CZ was synthesized by bilaterally linking phenothiazine dioxides to carbazoles via single bonds.Of these,the WX-G exhibits the highest external quantum efficiency（EQE）of 3.3%and the lowest turn-on voltage of 2.8 V.