高激子利用率的蓝光荧光材料及其激发态性质

Photophysical and Excited State Properties of Blue Fluorescent Material with High Exciton Utilizing Efficiency

制备了具有高激子利用率的A-π-D-π-A结构的蓝光荧光材料Cz PAF-CP,并通过紫外-可见吸收光谱和荧光光谱以及理论计算等方法对化合物的光物理性质及激发态性质进行了研究。该化合物表现出显著的溶剂化效应,溶剂化红移高达116 nm。根据Lippert-Mataga关系以及瞬态光谱测试证明CzPAF-CP具有局域电荷转移杂化态,这一点从理论计算结果也可以得到证明。由于CzPAF-CP具有扭曲A-π-D-π-A结构,在水含量高达90%的水和四氢呋喃混合溶液中荧光没有被猝灭,具有聚集诱导发光性质。以CzPAF-CP为发光材料制备的OLED器件发射蓝光,其电致发光光谱最大发射峰在452 nm,半峰宽54 nm,色坐标为(0. 150,0. 117)。最大外量子效率达到6. 3%,激子利用率达到71. 6%,超出25%的上限,这是由于CzPAF-CP局域电荷转移杂化态导致高能级单线态和三线态激子发生反系间窜越导致的。

Blue emissive fluorescent material CzPAF-CP based on A-π-D-π-A structure with high exciton utilizing efficiency was prepared. The photophysical and excited state properties of CzPAF-CP were mainly studied by the UV-vis absorption spectra, photoluminescence spectra and theoretical calculation. CzPAF-CP exhibits remarkable solvatochromic effect with a large bathochromic shift of 116 nm in different polar solvents. Further investigation according to Lippert-Mataga equation and transient photoluminescence decay spectra prove that CzPAF-CP possesses a hybridized local and charge transfer state, which can be confirmed by theoretical calculation. Due to the twisting A-π-D-π-A configuration, fluorescence from CzPAF-CP in water/THF mixture with high water fraction does not quench, displaying aggregation induced emission. The OLED using CzPAF-CP as emissive material emits blue light with emissive peak at 452 nm, full width at half maximum of 54 nm and Commission International de L＇Eclairage coordinates of （0.150, 0.117）. In addition, the device also achieved high efficiency with maximum external quantum efficiency of 6.3%. The resulting exiton utilizing efficiency was determined to be 71.6%, far beyond the theoretical limit for traditional fluorescent material（25%）. Such high exiton utilizing efficiency is ascribed to special exited state of hybridized local and charge transfer state and reverse intersystem crossing from triplet exitons to singlet excitons at higher energy level.