卤素原子的引入对二苯甲基自由基光稳定性、光物理性质及电致发光器件性能的影响

通过在N-咔唑基-二(2,4,6-三氯苯)甲基自由基(CzBTM)的咔唑基团的3和6位引入卤素原子, 合成了3个新的自由基分子(3,6-二氟-N-咔唑基)二(2,4,6-三氯苯)甲基自由基(F₂CzBTM)、 (3,6-二氯-N-咔唑基)二(2,4,6-三氯苯)甲基自由基(Cl₂CzBTM)及(3,6-二溴-N-咔唑基)二(2,4,6-三氯苯)甲基自由基(Br₂CzTM). 通过对比3个自由基分子与CzBTM的理论计算结果、 电化学性质、 光物理性质以及光稳定性, 发现对于电子给-受体型的发光自由基, 其光物理性质是外围取代基团的电负性和分子空间构型共同作用的结果. Cl₂CzBTM和Br₂CzTM具有较高的光致发光荧光量子效率, 而F₂CzBTM在光照下具有最长的光致发光半衰期. 与以CzBTM为发光层制备的电致发光器件相比, 以Cl₂CzBTM和Br₂CzTM为发光层制备的有机电致发光器件的光谱均发生了蓝移, 器件的最大外量子效率均有所提高, 分别是其1.8倍和2.5倍.

Effects of Introducing Halogen Atoms to Biphenylmethyl Radical on Photostability,Photophysical and Electroluminescent Properties †

Based on (N-carbazolyl)bis(2,4,6-trichlorophenyl) methyl(CzBTM), three new radicals, (3,6-difluoro-N-carbazoly)bis(2,4,6-trichlorophenyl) methyl (F₂CzBTM), (3,6-dichloro-N-carbazoly)bis(2,4,6-trichlorophenyl) methyl (Cl₂CzBTM) and (3,6-dibromo-N-carbazoly)bis(2,4,6-trichlorophenyl) methyl(Br₂CzBTM), were synthesized. By introducing the halogen atoms(F, Cl, Br) to the carbazole moiety, the electrochemical properties, theoretical calculation results, photophysical properties as well as photostability of the new radicals change obviously comparing with CzBTM. Cl₂CzBTM and Br₂CzBTM display higher photoluminescence quantum yield and F₂CzBTM exhibits the highest stability under a UV pulse laser irradiation. The organic light-emitting didoes(OLEDs) using Cl₂CzBTM and Br₂CzBTM as emitters were fabricated and the electroluminescence spectra of them are blue-shifted comparing with that of CzBTM. The maximum external quantum yield(EQE_max) of the devices based on Cl₂CzBTM and Br₂CzBTM are enhanced, which are 1.8 and 2.5 times that of CzBTM-based device, respectively.