Anomalous Light Emission and Wide Photoluminescence Spectra in Graphene Quantum Dot: Quantum Confinement from Edge Microstructure
Anomalous Light Emission and Wide Photoluminescence Spectra in Graphene Quantum Dot: Quantum Confinement from Edge Microstructure
复制标题
石墨烯量子点中的反常发光和宽光致发光光谱：边缘微结构的量子限制
DOI：
10.1021/acs.jpclett.6b01309
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发表时间：
2016-08-04
影响因子：
5.7
通讯作者：
Lut, Jing
中科院分区：
文献类型：
--
作者：
Huang, Pu;Shi, Jun-jie;Lut, Jing
多年来，人们一直在争论观察到的反常光致发光行为的物理根源，即大尺寸的石墨烯量子点(GQD)的光致发光能量高于小尺寸的石墨烯量子点，并且光致发光光谱从深紫外展宽到近红外。显然，它与广为接受的量子限制相冲突。在这里，我们通过基于多体微扰理论的最先进的第一原理计算，对这两个值得注意的辩论进行了新的解释。我们发现在具有显著尺寸依赖的激子吸收/发射的GQD中，量子限制是显著的。从碱性到酸性的边缘环境导致了发光峰的蓝移。此外，碳空位倾向于聚集在GQD边缘，形成微小的边缘微结构。位于这些边缘微结构中的束缚激子决定了大尺寸GQD的反常发光行为(蓝光和紫外光发射)。束缚激子限制在整个GQD中，导致低能跃迁。
The physical origin of the observed anomalous photoluminescence (PL) behavior, that is, the large-size graphene quantum dots (GQDs) exhibiting higher PL energy than the small ones and the broadening PL spectra from deep ultraviolet to near-infrared, has been debated for many years. Obviously, it is in conflict with the well-accepted quantum confinement. Here we shed new light on these two notable debates by state-of-the-art first-principles calculations based on many-body perturbation theory. We find that quantum confinement is significant in GQDs with remarkable size-dependent exciton absorption/emission. The edge environment from alkaline to acidic conditions causes a blue shift of the PL peak. Furthermore, carbon vacancies are inclined to assemble at the GQD edge and form the tiny edge microstructures. The bound excitons, localized inside these edge microstructures, determine the anomalous PL behavior (blue and UV emission) of large-size GQDs. The bound excitons confined in the whole GQD lead to the low energy transition.