Toward Tunable Electroluminescent Devices by Correlating Function and Submolecular Structure in 3D Crystals, 2D-Confined Monolayers, and Dimers.
Toward Tunable Electroluminescent Devices by Correlating Function and Submolecular Structure in 3D Crystals, 2D-Confined Monolayers, and Dimers.
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DOI：
10.1021/acsami.8b03528
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发表时间：
2018-06
影响因子：
9.5
通讯作者：
S. Wilde;Dongxin Ma;Tobias Koch;A. Bakker;Darío González-Abradelo;L. Stegemann;C. Daniliuc;H. Fuchs;Hongying Gao;N. Doltsinis;Lian Duan;C. Strassert
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作者：
S. Wilde;Dongxin Ma;Tobias Koch;A. Bakker;Darío González-Abradelo;L. Stegemann;C. Daniliuc;H. Fuchs;Hongying Gao;N. Doltsinis;Lian Duan;C. Strassert
报道了具有定制环金属C^N*N^C发光团的新型铂(II)配合物的合成及其光物理性质。当两个环金属化环上的两个C-H单元被N原子等规取代时，单体物种的发射可以发生蓝移。扫描隧道显微镜显示了它们在升华过程中的显著稳定性，这也揭示了一种明确的自组装行为，导致了超分子阵列的形成，在2D限制的单分子膜中显示出三重对称。超分子组织是由侧链的van der Waals相互作用驱动的，与发光团的性质无关，正如在晶相中观察到的那样，3D中没有明显的铂-铂相互作用。相反，在玻璃基质和非晶态固体中的发光性质表明分子间的相互作用和相当大的金属间耦合，这是通过(TD)DFT计算再现二聚体的发射光谱而得到的。循环伏安法也可以追踪到聚集的趋势，而热重分析证实了它们的稳定性。溶液处理和真空沉积的OLED器件显示出浓度依赖的电致发光，并随着掺杂比例的增加而红移。由于络合物的稳定性，溶液处理和真空沉积的器件显示出相同的电致发光光谱。除了有利于聚集，两个N原子的引入对器件性能也有不利的影响，因为激发态寿命延长有利于三重-三重态的湮灭。
The synthesis of new Pt(II) complexes bearing tailored cyclometalated C^N*N^C luminophores is reported along with their photophysical properties. The emission of the monomeric species can be blue shifted upon formal isosteric replacement of two C-H units by N atoms at the two cyclometalating rings. Their remarkable stability upon sublimation was demonstrated by means of scanning tunneling microscopy, which also revealed a defined self-assembly behavior leading to supramolecular arrays, showing a 3-fold symmetry in 2D-confined monolayers. The supramolecular organization is driven by van der Waals interactions of the side chains and does not depend on the nature of the luminophores, as also observed in the crystalline phases showing no significant Pt-Pt interactions in 3D. Conversely, the luminescence properties in glassy matrices at 77 K and in amorphous solids are indicative of intermolecular interactions with sizable intermetallic coupling, which was demonstrated by reproducing the emission spectra of dimeric species by means of (TD)DFT calculations. The tendency toward aggregation was also traceable by cyclic voltammetry, whereas thermogravimetric analyses confirmed their stability. Solution-processed and vacuum-deposited OLED devices showed a concentration-dependent electroluminescence that red shifts with increasing doping ratios. Due to the stability of the complexes, solution-processed and vacuum-deposited devices showed identical electroluminescence spectra. Besides favoring aggregation, introduction of two N atoms has a detrimental effect on the device performance, due to the prolonged excited-state lifetimes favoring triplet-triplet annihilation.