新型咔唑/喹啉基AIEE-TADF蓝光材料及其器件研究

Small-molecule and Polymer Based on Carbazole/Quinoline Derivatives Exhibiting AIEE and TADF Properties for Efficient Solution-processable Nondoped Blue OLEDs

以咔唑作为电子供体(D),喹啉作为电子受体(A),苯基间隔基作为π-桥,设计并构建了具有D-π-A结构的纯有机咔唑/喹啉衍生物—9-[4-(喹啉-8-基)苯基]-9H-咔唑(CPBA-Qx),并在所设计的蓝光小分子CPBA-Qx基础上,利用骨架-供体/悬垂-受体(BDPA)的设计策略,引入苯环作为间隔单元设计并合成了蓝光聚合物—聚[3-苯基-9-(4-(喹啉-8-基)苯基)-9H-咔唑](poly(CPBAQx-P)).对所合成材料的光物理性能研究表明,CPBA-Qx和poly(CPBAQx-P)在THF/H_(2)O混合溶液中均表现出典型的聚集诱导增强发射(AIEE)特征,二者的延迟寿命分别为1.25和1.09μs,出色的TADF特性与其具有较小的单-三重态能级差(ΔEST分别为0.11和0.16 eV)密不可分.基于CPBA-Qx和poly(CPBAQx-P)作为非掺杂发光层制备的溶液法加工OLED器件,其启亮电压(V_(on))和阈值电压(V_(th))分别为3.26/12 V、2.91/11 V,最大外量子效率(EQEmax)和国际照明委员会(CIE)坐标分别为5.24%和(0.19,0.12)、8.39%和(0.17,0.10).此外,在1000 cd·m^(−2)亮度下,基于poly(CPBAQx-P)的器件仍能高效发光(EQE=7.42%),效率滚降非常小,且具有窄半峰宽(FWHM)(59 nm)和CIE y值≤0.1.

A novel organic carbazolyl-quinoline derivative with D-π-A structure,9-[4-(quinoline-8-yl)phenyl]-9H-carbazole(CPBA-Qx),was designed and synthesized,in which carbazole was used as electron donor(D),quinoline as the electron acceptor(A)and phenyl spacer asπ-bridge.Based on the designed blue-emitting small-molecule CPBA-Qx,a blue-emitting polymer,poly[3-phenyl-9-(4-(quinoline-8-yl)phenyl)-9H-carbazole](poly(CPBAQx-P)),was designed and synthesized by Suzuki coupling copolymerization with donor as the main chain and acceptor as the side chain according to the molecular designing strategy of TADF polymer.Aggregation-induced enhanced emission(AIEE)performances of CPBA-Qx and poly(CPBAQx-P)were examined by studying the PL emission behaviour of their diluted mixtures in THF/H_(2)O with different water fractions(fw).Compared with pure solution,the study showed that the PL intensity and quantum yield(ΦPL)of CPBA-Qx and poly(CPBAQx-P)are significantly enhanced by 2‒10 times in the aggregate state,exhibiting typical AIEE characteristics.Meanwhile,both of them exhibited obviously delayed fluorescence with the lifetime of 1.25 and 1.09μs,accompanied by prompt fluorescence of 3.78 and 3.41 ns.For instance,the temperature-dependent transient photoluminescence spectra measured for CPBA-Qx and poly(CPBAQx-P)displayed enhanced delayed fluorescence upon the temperature rising from 100 K to 300 K,indicative of their TADF nature.The excellent TADF characteristics were closely related to extremely narrow singlet-triplet state energy splitting(ΔEST,CPBA-Qx 0.11 eV and poly(CPBAQx-P)0.16 eV).As a consequence,using CPBA-Qx and(poly(CPBAQx-P)as emitters,the turn-on voltage(V_(on))and threshold voltage(V_(th))of solution-processable nondoped OLEDs were 3.26/12 V and 2.91/11 V,respectively.The maximum external quantum efficiency(EQEmax)and Commission Internationale De L’Eclairage(CIE)coordinates were 5.24%and(0.19,0.12),8.39%and(0.17,0.10),respectively.Moreover,the non-doped OLED based on poly(CPBAQx-P)can retain high EL efficiency(EQE=7.42%)at 1000 cd·m^(−2),with small efficiency roll-off,a narrow full width at half maximum(FWHM=59 nm)and CIE y≤0.1.To sum up,poly(CPBAQx-P)as an emitter has great potential in solution-processed non-doped OLEDs,which lays experimental foundation for the application of AIEE-TADF polymer in OLEDs.