Study On The Synthesis And Electroluminescent Properties Of Polymers Containing Dibenzothiophene-s,s-dioxide Unit

In this thesis, blue-, green- and red-light-etmitting polymers containingdibenzothiophene-S,S-dioxide unit were designed and synthesized, and theirelectroluminescent properties were discussed.For the first time, 3,7-dibenzothiophene-S,S-dioxide unit was incorporated intopolyfluorene backbone to receive highly efficient and spectrally stable blue light-emittingmaterials. The EL spectra of the polymers were kept unchanged under variation of drivingcurrent densities and after annealing at different temperatures in a large range. PolymerPPF-3,7SO25 showed a turn-on voltage (Von), a maximum luminous efficiency (LEmax), amaximum external quantum efficiency (EQEmax) and a maximum luminance (Lmax) of 3.0 V,7.0 cd/A, 6.4% and 12080 cd/m~2, respectively, together with CIE coordinates of (0.17, 0.17).The LE declined slowly with increasing current densities. For example, a LE of 6.3 cd/A and aL of 6255 cd/m~2 were kept at 100 mA/cm~2, and a LE of 5.2 cd/A was still remained at 200mA/cm~2. PPF-3,7SO15 was also used as the host for a red phosphorescent emitter of Ir(piq)3,and the Von, LEmax, EQEmax, Lmax and CIE coordinates of 5.3 V, 7.7 cd/A, 13.4% and 7225cd/m~2 and (0.676, 0.318) were obtained. (Chapter 2)For the first time, 2,7-carbazole and 3,7-dibenzothiophene-S,S-dioxide binary copolymerswere prepared for blue light-emitting materials. The polymers not only maintained excellentspectral stability, but also showed a LEmax of 4.8 cd/A and an EQEmax of 3.6% together withCIE coordinates of (0.18, 0.32) with single device structure. (Chapter 3)Fluorene, 3,7-dibenzothiophene-S,S-dioxide and carbazole (2,7-linked or 3,6-linked)ternary copolymers were synthesized. Highly efficient blue light materials were obtained bychanging the linkage and carbazole content. Compared with polymers from chapter 2, thepolymers exhibited better EL proerties without PVK layer. Polymer PFSO15-2,7Cz10 had aVon of 3.1 V, and the LEmax, EQEmax and Lmax were 5.2 cd/A, 4.8% and 11372 cd/m~2,respectively. (Chapter 4)Blue light-emitting polymers were prepared by exploiting multi-functional units to further enhance the EL properties. For example, device based on PPF-TPA-Cz-SO10 showed aVon of 3.6 V and a LEmax of 5.6 cd/A. These polymers were also used as host forphosphorescent red emitters. A LEmax of 6.5 cd/A, an EQEmax of 10.9% and a Lmax of 5807cd/m~2 were obtained. (Chapter5)For the first time, alkylated 3,7-dibenzothiphene-S,S-dioxide and fluorene copolymerswere reported. It was found that the photophysical, electrochemical and EL properties could beeasily tuned by alkylation on DOSO and MOSO moiety. Compared with their parentcopolymers, the introduction of alkylated dibenzothiophene-S,S-dioxide imparted the resultingpolymers higher molecular weight, better solubility and better processibility. The color can betuned from blue to saturated blue via varying the number of octyl on SO unit. PolymerPF-3,7DOSO had a LEmax of 3.1 cd/A and an EQEmax of 3.9% with single layer devicestructure. It is worthy noting that the CIE cooridates were independent on the variation ofDOSO unit, thus imparting the resulting polymrs good reproducibility. (Chapter 6)From the chmical structure design perspective, fluorene and sidechain-typedibenzothiophene-S,S-dioxide copolymers were designed and prepared. SO unit was attachedon C-9 carbon of fluorene and N-9 of carbazole via a six alkyl tether. The donor unit (fluoreneand carbazole) and acceptor unit (dibenzothiophene-S,S-dioxide) were separated by alkyltether, thus reducing the intramolecular charge transfer effects on spectrum. (Chapter 7)A novel highly efficient green light-emitting hyperbranched phosphorescent polymerswith carbazole-alt-2,8-dioctyldibenzothiophene-S,S-dioxide as branch and Ir-complex as corewere synthesized. The two octyl groups on DOSO unit improved the solution processibility.The EL properties were enhanced dramatically due to the introduction of DOSO unit reducingthe LUMO levels of the resulting polymers. PCz-DOSOIr3 showed a LEmax of 35.5 cd/A,EQEmax of 13.8% and a Lmax of 16308 cd/m~2. Compared with the reference polymer PCzIr3,the LE was enhanced by up to 10-fold. Unlike many reports in the literatures usinglight-emitting materials (LEM) doping an electron-transporting materials, our device used solepolymer as LEM, which can avoid phase separation drawback. (Chapter 8)Poly(fluorene-co-3,7-dibenzothiophene-S,S-dioxide)s were used as host segment and DHTBT as red chromophore to obtain highly efficient red light-emitting polymers.PPFSO-DHTBT10 had a LEmax, an EQEmax, Lmax and CIE coordinates of 3.3 cd/A, 4.6%, 4479cd/m~2 and (0.67, 0.33), respectively. This is the best values for saturated red fluorescentpolymers in the literature. The EL performance can be further enhanced to 4.3 cd/A, 6.0% and4369 cd/m~2 by adding a PVK alyer. (Chapter 9)...