Solution-processable organic fluorescent dyes for multicolor emission in organic light emitting diodes
作者:Yong-Jin Pu、Makoto Higashidate、Ken-ichi Nakayama、Junji Kido
DOI:10.1039/b806160b
日期:——
Four novel fluorescent dyes, bis(difluorenyl)amino-substituted carbazole 1, pyrene 2, perylene 3, and benzothiadiazole 4, were synthesized by C–N cross-coupling with a palladium catalyst. These dyes are soluble in common organic solvents, and their uniform films were formed by spin-coating from their solutions. Their glass transition temperatures were sufficiently high (120–181 °C) to form amorphous films for organic light emitting diodes. These solution processable dyes exhibited strong photoluminescence (PL) in the film form (1: sky blue, 2: blue-green, 3: yellow, and 4: deep red). Optical and electrochemical properties of the compounds were investigated with photoelectron spectroscopy and cyclic voltammetry. The energy levels obtained from both measurements were in good agreement, and those levels were related to the electronic properties of the central core; the electron-donating carbazole compound showed the lowest ionization potential and the electron-withdrawing benzothiadiazole compound showed the largest electron affinity. Simple double layer devices were prepared with these fluorescent dyes as emitting layer and bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminium(III) (BAlq) as a common hole blocking layer for each color. Electroluminescence colors were the same as those of the PL spectra in each compound. These multicolor electroluminescences show that these conjugated oligomers can be candidates for solution processable light emitting materials for OLEDs as well as conjugated polymers or dendrimers.
通过钯催化的C-N交叉耦合反应合成了四种新型荧光染料,即双(二芴基)氨基取代的咔唑1、芘2、苝3和苯并噻二唑4。这些染料能溶于常见的有机溶剂,并通过旋涂法制备了它们的均匀膜。它们的玻璃化转变温度足够高(120-181 °C),足以形成用于有机发光二极管的非晶膜。这些可通过溶液法制备的染料在膜状态下呈现强烈的荧光发射(1:天蓝,2:蓝绿,3:黄色和4:深红)。通过光电子能谱和循环伏安法研究了所合成染料的光学和电化学性质。由这些测量得到的能级数据吻合良好,且发现这些能级与中心核的电子性质相关,其中给电子性的咔唑化合物表现出最低的电离势,而吸电子性的苯并噻二唑化合物表现出最大的电子亲和能。分别以这些荧光染料和双(2-甲基-8-喹啉酸)(对联苯酚酸)铝(III)(BAlq)为发射层和公共的空穴阻挡层制备了简单的双层器件。器件电致发光的颜色与每种染料的荧光光谱颜色相同。这些多色电致发光表明,这些共轭齐聚物不仅是共轭高分子或树枝状聚合物,也可以成为适用于有机电致发光材料的溶液可加工材料。