Fitting the magnetoresponses of the OLED using polaron pair model to obtain spin-pair dynamics and local hyperfine fields.
Fitting the magnetoresponses of the OLED using polaron pair model to obtain spin-pair dynamics and local hyperfine fields.
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DOI：
10.1038/s41598-020-73953-w
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发表时间：
2020-10-08
影响因子：
4.6
通讯作者：
Kreouzis T
中科院分区：
文献类型：
--
作者：
Weng Z;Gillin WP;Kreouzis T
当施加的磁场范围减小到亚毫特斯拉范围时，有机发光二极管（OLED）表现出符号反转磁场效应（MFE），并且极化子对模型已经成功地解释了超小MFE。在这里，我们在 ± 500 µT 的磁场范围内获得了三（8-羟基喹啉）铝基（Alq3）OLED 的高分辨率（~ 1 µT）磁导（MC）和磁电致发光（MEL），并且消除了地磁场分量。观察到一个清晰的“W”形 MC，其倾角位置为 ± 250 µT 和单调的 MEL。我们演示了一种使用极化子对模型对实验获得的 MC 和 MEL 进行拟合的技术。拟合过程提取工作 OLED 中物理上重要的参数：Alq3 中电子和空穴的局部超精细场：Bhf1 = (0.63 ± 0.01) mT（电子），Bhf2 = (0.24 ± 0.01) mT（空穴）；单线态和三线态极化子对的分离率：kS,s = (44.59 ± 0.01) MHz，kT,s = (43.97 ± 0.01) MHz，单线态极化子对的复合率 kS,r = (88 ± 6) MHz。产生的参数在不同的 OLED 中具有高度的可重复性，并且与密度泛函理论 (DFT) 计算和报告的实验观察结果广泛一致。这证明了这种拟合技术可以接近任何工作 OLED 以获得重要的微观参数。
Organic light-emitting diode (OLED) displays a sign reversal magnetic field effect (MFE) when the applied magnetic field range is reduced to the sub-milliTesla range and the Polaron Pair Model has been successful in explaining the ultra-small MFE. Here, we obtained high resolution (~ 1 µT) magnetoconductance (MC) and magnetoelectroluminescence (MEL) of a tris-(8-hydroxyquinoline)aluminium-based (Alq3) OLED within the magnetic field range of ± 500 µT with the earth magnetic field components cancelled. A clear “W” shaped MC with a dip position of ± 250 µT and a monotonic MEL were observed. We demonstrate a fitting technique using the polaron pair model to the experimentally obtained MC and MEL. The fitting process extracts physically significant parameters within a working OLED: the local hyperfine fields for electron and hole in Alq3: Bhf1 = (0.63 ± 0.01) mT (electron), Bhf2 = (0.24 ± 0.01) mT (hole); the separation rates for singlet and triplet polaron pairs: kS,s = (44.59 ± 0.01) MHz, kT,s = (43.97 ± 0.01) MHz, and the recombination rate for singlet polaron pair kS,r = (88 ± 6) MHz. The yielded parameters are highly reproducible across different OLEDs and are in broad agreement with density functional theory (DFT) calculations and reported experimental observations. This demonstrates the feasibility of this fitting technique to approach any working OLED for obtaining significant microscopic parameters.
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