材料科学
激发态
有机发光二极管
激子
电致发光
单重态
光致发光
荧光
量子效率
光电子学
电子
三苯胺
分子物理学
接受者
原子物理学
纳米技术
光学
凝聚态物理
物理
量子力学
图层(电子)
作者
Weijun Li,Yuyu Pan,Ran Xiao,Qiming Peng,Shitong Zhang,Dongge Ma,Feng Li,Fangzhong Shen,Yinghui Wang,Bing Yang,Yuguang Ma
标识
DOI:10.1002/adfm.201301750
摘要
In principle, the ratio (Φ) of the maximum quantum efficiencies for electroluminescence (EL) to photoluminescence (PL) can be expected to approach unity, if the exciton (bound electron–hole pair) generated from the recombination of injected electrons and holes in OLEDs has a sufficiently weak binding energy. However, seldom are examples of Φ > 25% reported in OLEDs because of the strongly bound excitons for most organic semiconductors in nature. Here, a twisting donor–acceptor triphenylamine‐thiadiazol molecule (TPA‐NZP) exhibits fluorescent emission through a hybridized local and charge‐transfer excited state (HLCT), which is demonstrated from both fluorescent solvatochromic experiment and quantum chemical calculations. The HLCT state possesses two combined and compatible characteristics: a large transition moment from a local excited (LE) state and a weakly bound exciton from a charge transfer (CT) state. The former contributes to a high‐efficiency radiation of fluorescence, while the latter is responsible for the generation of a high fraction of singlet excitons. Using TPA‐NZP as the light‐emitting layer in an OLED, high Φ values of 93% (at low brightness) and 50% (at high brightness) are achieved, reflecting sufficient employment of the excitons in the OLED. Characterization of the EL device shows a saturated deep‐red emission with CIE coordinates of (0.67, 0.32), accompanied by a rather excellent performance with a maximum luminance of 4574 cd m −2 and a maximum external quantum efficiency (η ext ) of ∼2.8%. The HLCT state is a new way to realize high‐efficiency of EL devices.
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