新型含咔唑聚芴类共轭聚电解质及其前驱体的合成与光电性能

Synthesis and Optical and Electroluminescent Properties of Novel Polyfluorene/Carbazole-based Conjugated Polyelectrolytes and Their Precursors

采用Suzuk i偶合反应成功地合成了一系列在主链上具有不同含量苯并噻二唑单元的聚咔唑和含胺基芴的衍生物:聚[3,6-(N-(2-乙基己基))咔唑-2,1,3-苯并噻二唑-9,9-双(N,N-二甲基胺丙基)芴](PCzN-BTDZ);通过对所得聚合物的季铵盐化后处理得到了其相应的聚电解质衍生物:聚[3,6-(N-(2-乙基己基))咔唑-2,1,3-苯并噻二唑-9,9-(双(3-(′N,N-二甲基)-N-乙基铵)丙基)芴]二溴(PCzNB r-BTDZ)。通过对它们的电致发光性能的研究,发现所有的聚合物用高功函数铝作阴极的器件具有和用钡/铝作阴极的器件相近的发光性能,说明这类聚合物具有良好的电子注入性能。不同比例的2,1,3-苯并噻二唑(BTDZ)的引入使聚合物中发生有效的能量转移,调节了聚合物的发光颜色;同时也提高了聚合物的器件性能。其中聚合物PCzN-BTDZ1在器件结构为ITO/PEDOT/PVK/Polym er/BaA l时的效率达0.99%,高于PCzN在相同器件结构时的效率(0.14%)。

With their ionic side groups being attached to the conjugated main chain, conjugated polyelectrolytes （CPs） can offer particular properties compared with the normal ＂neutral＂ polymers, having attracted considerable attention in recent years. Generally speaking, there are only a few reports on electroluminescent properties of LEDs fabricated from CPs. Previously, our group has reported the first LEDs based on ammonium functioned polyfluorene electrolytes, and a series of high-efficiency, environment-friendly electroluminescent polymers. With their terminal amino groups and quaternized ammonium groups, the devices from such polymers show the excellent electron injection ability. As a good performance of a device requires the balance between the hole and electron transporting in the emissive layer, it can feasible to synthesize polymers containing hole-transporting units on the basis of our previous work. It is well-known that carbazole-containing polymers are good hole-transporting materials due to the electron-donating capabilities associated with the nitrogen in the carbazole. A series of novel aminoalkyl-substituted fluorene/carbazole based main chain copolymers with benzothiadiazole （BTDZ） of different content were synthesized by Suzuki coupling reaction： poly [ 3,6-（ N-（ 2-ethylhexyl） carbazole ） -（ 9,9-bis （ 3＇-（ N, N-dimethylamino ） propyl ） -2,7-fluorene ） - 4, 7-（ 2, 1,3-benzothiadiazole） ] （PCzN-BTDZ）. Through a postpolymerization treatment on the terminal amino groups, their quaternized ammonium polyelectrolyte derivatives were obtained： poly [ 3,6-（N-（2-ethylhexyl） carbazole）- （9,9-bis （ 3＇- （ （ N, N-dimethyl ） - N- ethylammonium ） propyl ） -2,7- fluorene ） - 4,7- （ 2,1,3-benzothiadiazole ） ] dibromide （PCzN-BTDZBr）. It was found that devices from such polymers with the high work-function metal cathode such as Al show similar device performance to that by using the low work-function cathode such as Ba, indicating the excellent electron injection ability of these polymers. And it was observed that the efficient energy transfer occurs by exciton trapping on the narrow band gap BTDZ site for both the neutral and the quaternized copelymers. The addition of BTDZ comonomer also improves their PLED devices performance. When PEDDT/PVK was used as an anode buffer, the external quantum efficiency is higher than that of the copolymer PCzN in the same device of the copolymer PCzN-BTDZ1 is 0.99%, which configuration.