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Employing ～100% Excitons in OLEDs by Utilizing a Fluorescent Molecule with Hybridized Local and Charge-Transfer Excited State

机译：利用具有局部和电荷转移激发态混合态的荧光分子在OLED中使用约100％的激子

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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.
机译：原则上，如果激子（束缚的电子-空穴对）是由注入的电子和空穴的复合产生的，则可以预期电致发光（EL）与光致发光（PL）的最大量子效率之比（Φ）接近1。 OLED具有足够弱的结合能。但是，由于自然界中大多数有机半导体的激子都具有牢固结合的激子，因此在OLED中很少出现Φ＞ 25％的例子。在这里，扭曲的供体-受体三苯胺-噻二唑分子（TPA-NZP）通过混合的局部和电荷转移激发态（HLCT）显示荧光发射，这从荧光溶剂变色实验和量子化学计算中得到证明。 HLCT状态具有两个组合且兼容的特性：从局部激发（LE）状态的跃迁矩大，以及从电荷转移（CT）状态的弱束缚激子。前者有助于荧光的高效辐射，而后者则负责产生高比例的单重态激子。使用TPA-NZP作为OLED中的发光层，可以获得93％（在低亮度下）和50％（在高亮度下）的高Φ值，这反映了在OLED中充分利用了激子。 EL器件的表征显示出饱和的深红色发射，其CIE坐标为（0.67，0.32），同时具有相当出色的性能，最大亮度为4574 cd m〜2，最大外部量子效率（η_（ext）） 〜2.8％。 HLCT状态是实现EL器件高效率的新途径。

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  • 来源
    《Advanced Functional Materials》 |2014年第11期|1609-1614|共6页
  • 作者

    Weijun Li; Yuyu Pan; Ran Xiao; Qiming Peng; Shitong Zhang; Dongge Ma; Feng Li; Fangzhong Shen; Yinghui Wang; Bing Yang; Yuguang Ma;

  • 作者单位

    State Key Lab of Supramolecular Structure and Materials Jilin University 2699 Qianjin Avenue, Changchun, 130012, PR China;

    State Key Lab of Supramolecular Structure and Materials Jilin University 2699 Qianjin Avenue, Changchun, 130012, PR China;

    State Key Lab of Supramolecular Structure and Materials Jilin University 2699 Qianjin Avenue, Changchun, 130012, PR China;

    State Key Lab of Supramolecular Structure and Materials Jilin University 2699 Qianjin Avenue, Changchun, 130012, PR China;

    State Key Lab of Supramolecular Structure and Materials Jilin University 2699 Qianjin Avenue, Changchun, 130012, PR China;

    State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun, 130022, PR China;

    State Key Lab of Supramolecular Structure and Materials Jilin University 2699 Qianjin Avenue, Changchun, 130012, PR China;

    State Key Lab of Supramolecular Structure and Materials Jilin University 2699 Qianjin Avenue, Changchun, 130012, PR China;

    State Key Lab of Supramolecular Structure and Materials Jilin University 2699 Qianjin Avenue, Changchun, 130012, PR China;

    State Key Lab of Supramolecular Structure and Materials Jilin University 2699 Qianjin Avenue, Changchun, 130012, PR China;

    State Key Lab of Supramolecular Structure and Materials Jilin University 2699 Qianjin Avenue, Changchun, 130012, PR China;

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