Design,Synthesis And Performance Of Polystyrene-Based Through-Space Charge Transfer Polymers

Through-space charge transfer(TSCT)polymers where electronic donor and electronic acceptor are spatially separated,can exhibit spatial n-n interaction and charge transfer emission from adjacent donor and acceptor as well as thermally activated delayed fluorescence(TADF)effect,providing a new strategy to develop highly-efficient fluorescent polymers.This thesis is focused on addressing two key issues for polystyrene-based TSCT polymers including tuning their emission color and enhancing their luminescence efficiency.By modulating the spatial interaction between donor and acceptor,polystyrene TSCT polymers with full-color and white emissions are developed.Meanwhile,by employing polystyrene TSCT polymers as sensitizers for fluorescent chromophore,high-efficiency and full-color fluorescent polymers are developed.1.By using acridan unit as donor and triazine derivatives as acceptor to tune charge transfer strength between donor and acceptors with different electron-accepting ability,polystyrene TSCT polymers with emission color spanning from deep blue to red(emission wavelength from 453 to 616 nm)can be achieved.The resultant TSCT polymers exhibit TADF effect with delayed fluorescence lifetime of 0.36-1.28μs,thus triplet excitons can be converted into singlet ones and utilized for emission.Soluton-processed organic lighting-diodes(OLEDs)based on TSCT polymers give external quantum efficiencies of 12.1%,16.2%and 1.0%for blue,green and red emission.2.By introducing one acridan donor(Ac,D)and two triazine acceptors(TRZ-H(A1)and TRZCN(A2))into polystyrene to form two donor/acceptor pairs(Ac/TRZ-H and Ac/TRZ-CN),single white-emitting fluorescent polymers with duplex through-space charge transfer channels(blue and yellow channels)are developed,exhibiting the highest external quantum efficiency of 14.1%and power efficiency of 34.8 Im W-1 with coordinates of(0.38,0.43).Meanwhile,single white-emitting polymers are designed by using blue TSCT polymer as host for yellow phosphor which simultaneously exhibit blue delayed fluorescence from polymer host and yellow phosphorescence from phosphor unit.As both TSCT polymer host and phosphor unit can harvest triplet excitons,a high power efficiency of 42.8 Im W-1 can be realized.Moreover,the reverse intersystem crossing process of TSCT polymer host can reduce triplet exciton density and suppress triplet-triplet annihilation at high luminance,leading to a small efficiency roll-off of 1.9%at luminance of 1000 cd m-2 for resultant white-emitting polymers3.By employing TSCT polystyrenes as host for blue,green and red chromophore(3-phenylperylene,tetrakis(4-tert-butylphenyl)anthracene-9,10-diamine and 4-(9-(4-methoxyphenyl)naphthothiadiazol-4-yl)-N,N-diphenylaniline),high-efficiency and full-color fluorescent polymers are developed,which combines the advantages of high exciton utilization efficiency of TSCT polymer and high photoluminance yield of fluorescent emitter.Solution-processed OLEDs based on the polymers reveal maximum external quantum efficiencies of 14.6%,19.2%and 10.3%for blue,green and red emission,respectively,which are 4.4-5.0 folds higher than those of corresponding control polymers.Meanwhile,by introducing bridge atoms to triphenylamine donor to enhance molecular rigidity,TSCT polystyrene hosts with low non-radiative decay rates are developed.Solution-processed OLEDs using the TSCT polymer as host and red fluorescent chromophore(tetraphenyldibenzoperiflanthene(DBP))as emitter exhibit red emission with maximum external quantum efficiency of 9.9%and CIE(0.62,0.37).