Rational Design of Strongly Blue-Emitting Cuprous Complexes with Thermally Activated Delayed Fluorescence and Application in Solution-Processed OLEDs
Rational Design of Strongly Blue-Emitting Cuprous Complexes with Thermally Activated Delayed Fluorescence and Application in Solution-Processed OLEDs
复制标题
具有热激活延迟荧光的强蓝光亚铜配合物的合理设计及其在溶液加工OLED中的应用
DOI：
10.1021/cm4024309
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发表时间：
2013-10-08
影响因子：
8.6
通讯作者：
Lu, Can-Zhong
中科院分区：
文献类型：
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作者：
Chen, Xu-Lin;Yu, Rongmin;Lu, Can-Zhong
含N-连接的2-吡啶基吡唑二亚胺配体[Cu(Pypz)(Op)]BF4(1)，[Cu(Pyppz)(Op)]BF4(2)和[Cu(Pytfmpz)(Op)]BF4(2)，[Cu(Pytfmpz)(Op)]BF4(3)(pypz=1-(2-吡啶)吡唑，pympz=3-甲基-1-(2-吡啶)吡唑，Pympz=1-(2-吡啶)吡唑，并设计合成了3-三氟甲基-1-(2-吡啶)吡唑)。表征了它们的结构、电化学性质和光物理性质。在室温下，配合物1-3在氮气饱和的CH2Cl2(高达45%)和纯净固体(高达87%)中都表现出高的光致发光量子产率(PLQY)，这与报道的CuProus配合物的最高值相当。光谱性质和发射衰减行为的温度依赖关系揭示了两个热平衡发射态的存在。在低于150K的温度下，最低的三重态(T-1)是主要的发射态，导致典型的磷光发射，发射衰减时间在数百微秒量级。然而，在常温下，仅位于T-1态上方约0.17-0.18 eV的最低单线态(S-1)被热填充，进而产生有效的热激活延迟荧光(TADF)，发射衰减时间急剧减少到例如12.2微米S 2。在发射层中含有1-3的溶液处理OLED通过利用单态捕获机制展示了优异的器件性能，其中使用3的电致发光器件显示出8.47%的峰值外量子效率。峰值电流效率为23.68 cd/A，最大亮度为2033 cd/m(2)。
A new series of strongly greenish-blue to blue emitting Cu(NN)(POP)(+) (POP = bis[2-(dipenylphosphino)phenyl]ether) complexes containing N-linked 2-pyridyl pyrazolate diimine ligands [Cu(pypz)(POP)]BF4 (1), [Cu(pympz)(POP)]BF4 (2), and [Cu(pytfmpz)(POP)]BF4 (3) (pypz = 1-(2-pyridyl)pyrazole, pympz = 3-methyl-1-(2-pyridyl)pyrazole, and pytfmpz = 3-trifluoromethyl-1-(2-pyridyl)pyrazole) have been designed and synthesized. Their structural, electrochemical, and photophysical properties have been characterized. The complexes 1-3 exhibit high photoluminescence quantum yields (PLQYs) at room temperature both in nitrogen-saturated CH2Cl2 (up to 45%) and in neat solid (up to 87%), which are comparable to the reported highest values for the cuprous complexes. The temperature dependence of spectroscopic properties and emission decay behaviors reveal the presence of two thermally equilibrated emitting states. At temperatures below 150 K, the lowest triplet state (T-1) is the predominant emitting state resulting in the typical phosphorescence with the emission decay times in the order of hundreds of microseconds. However, at ambient temperature, the lowest singlet state (S-1), which lies only about 0.17-0.18 eV above the T-1 state, is populated thermally and in turn generates efficient thermally activated delayed fluorescence (TADF), and the emission decay times are reduced dramatically to, e.g., 12.2 mu s for 2. Solution-processed OLEDs containing 1-3 in the emissive layer demonstrated excellent device performances by taking advantage of the singlet harvesting mechanism, among which the electroluminescent device using 3 shows a peak external quantum efficiency (EQE) of 8.47%, a peak current efficiency (CE) of 23.68 cd/A, and a maximum brightness of 2033 cd/m(2).