Effect of substitution of methyl groups on the luminescence performance of IrIII complexes:: Preparation, structures, electrochemistry, photophysical properties and their applications in organic light-emitting diodes (OLEDs)
Effect of substitution of methyl groups on the luminescence performance of IrIII complexes:: Preparation, structures, electrochemistry, photophysical properties and their applications in organic light-emitting diodes (OLEDs)
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DOI：
10.1002/ejic.200400114
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发表时间：
2004-09-06
影响因子：
2.3
通讯作者：
Kwon, SK
中科院分区：
文献类型：
--
作者：
Jung, SG;Kang, YJ;Kwon, SK
一系列二甲基取代三（吡啶基苯基）铱（III）衍生物[(n- mepy -n'-MePh)(3)Ir] [n = 3, n' = 4 (1)]；N = 4, N ' = 4 (2)；N = 4, N ' = 5 (3)；N = 5, N ' = 4 (4)；合成了N = 5, N ' = 5(5)]，并对其进行了表征，以研究甲基取代对固体结构和光致发光的影响。系统地评价了1-5的吸收、发射、循环伏安和电致发光性能。2和4的结构已通过单晶x射线衍射分析确定。在甘油溶液回流（bbb200℃）下，主要形成具有扭曲八面体几何形状的面型络合物，是所有情况下的主要成分。电化学研究表明，相对于Ir(ppy)(3) （ppy = 2-苯基吡啶），氧化电位要小得多。所有配合物都表现出强烈的绿色光致发光（PL），这归因于金属到配体电荷转移（MLCT）三重态发射。配合物1、3、4和5的薄膜在室温下的最大发射波长在529 ~ 536 nm之间，而配合物2呈现蓝移发射带（λ (max) = 512 nm），其PL量子效率（phi(PL) = 0.52）高于配合物1和3-5；这是由于分子间相互作用的减少。用三种（2,3和4）Ir-III衍生物作为掺杂材料制备了多层有机发光二极管（oled）。器件的电致发光（EL）光谱在509 ~ 522 nm处有最大峰，肩峰在552 nm附近，与298 K溶液中的发光光谱一致。器件显示工作电压为1ma /cm(2)，分别为Ir(ppy)(3)、2、3和4的4.9、5.6、5.1和4.6 V。特别是，具有2的器件显示出比Ir(ppy)(1 mA/cm(2)时更高的外量子效率(在1 mA/cm（2)时eta(ext) = 11%）和亮度(在20 mA/cm(2)时4543 cd/m(2))(eta(ext) = 6.0%)；在20ma /cm(2)下的3156 cd/m(2)和其他Ir(dmppy)(3)衍生物（dmppy =二甲基取代的ppy）在相同的条件下。金属原子的间位（Ph）和对位（Py）上的甲基对金属原子的吸收、发射、氧化还原电位和电致发光有很大的影响。(C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004。
A series of dimethyl-substituted tris(pyridylphenyl)iridium(III) derivatives [(n-MePy-n'-MePh)(3)Ir] [n = 3, n' = 4 (1); n = 4, n' = 4 (2); n = 4, n' = 5 (3); n = 5, n' = 4 (4); n = 5, n' = 5 (5)] have been synthesized and characterized to investigate the effect of the substitution of methyl groups on the solid-state structure and photo- and electroluminescence. The absorption, emission, cyclic voltammetry and electroluminescent performance of 1-5 have also been systematically evaluated. The structures of 2 and 4 have been determined by a single-crystal X-ray diffraction analysis. Under reflux (> 200 degreesC) in glycerol solution, fac-type complexes with a distorted octahedral geometry are predominantly formed as the major components in all cases. Electrochemical studies showed much smaller oxidation potentials relative to Ir(ppy)(3) (Hppy = 2-phenylpyridine). All complexes exhibit intense green photoluminescence (PL), which has been attributed to metal-to-ligand charge transfer (MLCT) triplet emission. The maximum emission wavelengths of thin films of 1, 3, 4 and 5 at room temperature are in the range 529-536 nm, while 2 displays a blue-shifted emission band (lambda(max) = 512 nm) with a higher PL quantum efficiency (phi(PL) = 0.52) than those of complexes 1 and 3-5; this is attributed to a decrease of the intermolecular interactions. Multilayered organic light-emitting diodes (OLEDs) were fabricated by using three (2, 3 and 4) of these Ir-III derivatives as dopant materials. The electroluminescence (EL) spectra of the devices, which have the maximum peaks at 509-522 nm, with shoulder peaks near 552 nm, are consistent with the PL spectra in solution at 298 K. The devices show operating voltages at 1 mA/cm(2) of 4.9, 5.6, 5.1, and 4.6 V for Ir(ppy)(3), 2, 3, and 4, respectively. In particular, the device with 2 shows a higher external quantum efficiency (eta(ext) = 11 % at 1 mA/cm(2)) and brightness (4543 cd/m(2) at 20 mA/cm(2)) than Ir(ppy)(3) (eta(ext) = 6.0% at 1 mA/cm(2); 3156 cd/m(2) at 20 mA/cm(2) and other Ir(dmppy)(3) derivatives, (dmppy = dimethyl-substituted ppy), under the same conditions. The methyl groups at the meta (Ph) and para (Py) positions to the It metal atom have a great influence on absorption, emission, redox potentials and electroluminescence. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.