Nearly 100% Internal Quantum Efficiency in an Organic Blue‐Light Electrophosphorescent Device Using a Weak Electron Transporting Material with a Wide Energy Gap
Nearly 100% Internal Quantum Efficiency in an Organic Blue‐Light Electrophosphorescent Device Using a Weak Electron Transporting Material with a Wide Energy Gap
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DOI：
10.1002/adma.200802034
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发表时间：
2009-03
影响因子：
29.4
通讯作者：
Lixin Xiao;Shi-jian Su;Y. Agata;Hsinglin Lan;J. Kido
中科院分区：
文献类型：
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作者：
Lixin Xiao;Shi-jian Su;Y. Agata;Hsinglin Lan;J. Kido
有机电致发光器件（OLED）的高效率是推动OLED在下一代平板显示器中应用的关键因素。在OLED中，光的产生是空穴与从电极注入的有机发光材料（EM）内的电子复合的结果。因此，OLED的效率由空穴与电子的复合效率和EM的光致发光量子产率组成。基于OLED的常规分层结构，可以获得1/（2 n 2）的发射提取效率（其中n是有机材料的折射率，其约为1.6 [1]）。在发光体的情况下，25%的内部量子效率（IQE，其对应于5%的外部量子效率（EQE））可以从25%的单重自旋状态获得。当应用磷光发射体时，剩余的75%的三重态自旋态也可以发光。因此，理论上可获得100%的IQE（相当于EQE的20%）。[2]事实上，在使用磷光染料双（2-苯基吡啶基）乙酰丙酮合铱（III）[（ppy）2 Ir（acac）]作为发射体的绿光电磷光装置中获得了（87（cid：2）7）%的IQE（其对应于约19%的EQE）。[3]最近，使用fac三（2-苯基吡啶）铱获得了接近理论极限的绿光发射（超过20%的EQE）
High efficiency in organic light-emitting devices (OLEDs) is a crucial factor to promote the application of OLEDs in the next generation of flat panel displays. In an OLED, the generation of light is the consequence of the recombination of holes with electrons within the organic emitting material (EM) injected from the electrodes. Therefore, the efficiency of an OLED is composed of the recombination efficiency of holes with electrons and the photoluminescence quantum yield of the EM. Based on the conventional layered structure of an OLED, an emission extraction efficiency of 1/(2 n 2 ) can be obtained (where n is the refractive index of the organic material, which is about 1.6 [1] ). In the case of a fluorescent emitter, 25% of internal quantum efficiency (IQE, which corresponds to (cid:1) 5% of an external quantum efficiency (EQE)) can be obtained from the 25% of singlet spin states. When a phosphorescent emitter is applied, the remainder 75% of triplet spin states can also emit light. Therefore, an IQE of 100% (which corresponds to (cid:1) 20% of EQE) can theoretically be obtained. [2] In fact, (87 (cid:2) 7)% of an IQE (which corresponds to about 19% of an EQE) was obtained in a green-light electrophosphorescent device using a phosphorescent dye, bis(2-phenylpyridinato)iridium( III ) acetylacetonate [(ppy) 2 Ir (acac)], as the emitter. [3] Recently, a near theoretical limitation of green-light emission (over 20% of EQE) was obtained using fac tris(2-phenylpyridinato)iridium