Xu Junwei, Cui Yue, Smith Gregory M, Li Peiyun, Dun Chaochao, Shao Linqi, Guo Yang, Wang Hongzhi, Chen Yonghua, Carroll David L
1Center for Nanotechnology and Molecular Materials, Wake Forest University, Winston-Salem, NC 27109 USA.
2Department of Physics, Wake Forest University, Winston-Salem, NC 27106 USA.
Light Sci Appl. 2018 Aug 1;7:46. doi: 10.1038/s41377-018-0046-5. eCollection 2018.
In this work, we show that the spin dynamics of excitons can be dramatically altered by Maxwell magnetic field coupling, together with an ion-enhanced, low-internal-splitting-energy organic semiconducting emitter. By employing a unique, alternating current (AC)-driven organic electroluminescent (OEL) device architecture that optimizes this magnetic field coupling, almost complete control over the singlet-to-triplet ratio (from fluorescent to phosphorescent emission in a single device) is realized. We attribute this spin population control to magnetically sensitive polaron-spin pair intersystem crossings (ISCs) that can be directly manipulated through external driving conditions. As an illustration of the utility of this approach to spin-tailoring, we demonstrate a simple hybrid (double-layer) fluorescence-phosphorescence (F-P) device using a polyfluorene-based emitter with a strong external Zeeman effect and ion-induced long carrier diffusion. Remarkable control over de-excitation pathways is achieved by controlling the device-driving frequency, resulting in complete emission blue-red color tunability. Picosecond photoluminescence (PL) spectroscopy directly confirms that this color control derives from the magnetic manipulation of the singlet-to-triplet ratios. These results may pave the way to far more exotic organic devices with magnetic-field-coupled organic systems that are poised to usher in an era of dynamic spintronics at room temperature.
在这项工作中，我们表明，激子的自旋动力学可通过麦克斯韦磁场耦合以及离子增强的、低内部分裂能的有机半导体发射体而发生显著改变。通过采用一种独特的、交流（AC）驱动的有机电致发光（OEL）器件架构来优化这种磁场耦合，实现了对单重态与三重态比率（在单个器件中从荧光发射到磷光发射）的几乎完全控制。我们将这种自旋布居控制归因于磁敏极化子 - 自旋对的系间窜越（ISC），其可通过外部驱动条件直接操控。作为这种自旋剪裁方法实用性的一个例证，我们展示了一种简单的混合（双层）荧光 - 磷光（F - P）器件，该器件使用具有强外部塞曼效应和离子诱导长载流子扩散的聚芴基发射体。通过控制器件驱动频率，实现了对去激发途径的显著控制，从而实现了完整的发射蓝 - 红颜色可调性。皮秒光致发光（PL）光谱直接证实，这种颜色控制源于单重态与三重态比率的磁操控。这些结果可能为具有磁场耦合有机系统的更为奇特的有机器件铺平道路，这些器件有望开启室温下动态自旋电子学的时代。
