基于新型腈类染料的白色有机电致发光器件的光谱特性

Spectral Characteristics of White Organic Light-Emitting Devices Based on a Novel Nitrile Fluorescence Dye

将腈类黄色荧光染料(2Z,2’Z)-3,3-’(1,4-phenylene)bis(2-phenylacrylonitrile)(BPhAN)掺杂到poly(N-vinylcarbazole)(PVK)中作发光层,2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline(BCP)作电子传输层和空穴阻挡层,制备了结构为Indium-tin oxide(ITO)/PVK∶BPhAN/BCP/Mg∶Ag的双层有机电致发光器件。通过调节BPhAN掺杂质量百分比(2 wt%,4 wt%,6 wt%),测试了器件在不同电压下的光谱特性,研究了F rster能量转移和直接载流子俘获在发光过程中的作用。结果表明,当掺杂浓度为4 wt%时可实现色度较好的白光,随着电压从6 V增大到16 V,CIE色坐标从(0.33,0.37)变化到(0.32,0.33),在白光区域有微小蓝移,这是由于随着电压的增大,能量转移效率和直接载流子俘获效率都降低,BPhAN黄光减弱,PVK发射的蓝光增强。

A white organic light-emitting device with a blend polymeric emissive system consisting of a novel nitrile fluorescence （2Z, 2＇ Z）-3, 3＇-（1,4-phenylene） bis（2-phenylacrylonitrile） （BPhAN） as dopant and poly（N-vinylcarbazole） （PVK） as host was fabricated. 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline （BCP） was introduced into bilayer device as an electron transporting layer （HTL） and a hole blocking layer （HBL）, respectively. By adjusting the doping ratio of BPhAN, a series of devices with different concentration proportion of PVK ： BPhAN were constructed. The photol （PL） and electrol （EL） characteristics of the devices were systemically studied. The Forster energy transfer mechanisms and direct carrier trapping mechanisms were specially investigated. The results showed that effective Forster energy transfer from PVK to BPhAN existed in the blending system as well as carrier trapping. However, at the identical bias voltage, the performance of devices was affected mainly by the carrier trapping mechanisms. Nevertheless, at different bias voltages, the performance of devices was affected by both of the two mechanisms. When the doping ratio of BPhAN reached 4 wt%, bright white light was obtained. The peaks of EL spectra were located at 425 and 556 nrn corresponding to the Commissions Internationale De L＇ Eclairage （CIE） coordinates of （0.33, 0. 37） at 6 V and （0. 32, 0. 33） at 16 V, respectively. The slight shift of CIE coordinates was attributed to that energy transfer probability from PVK to BPhAN and BPhAN charge carrier trapping efficiency both decreased with the increase in voltages.