Li Ruifeng, Schneider Lorenz Maximilian, Heimbrodt Wolfram, Wu Huizhen, Koch Martin, Rahimi-Iman Arash
Department of Physics and the State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou, 310027, P.R. China.
Faculty of Physics and Materials Sciences Center, Philipps-Universität Marburg, 35032 Marburg, Germany.
Sci Rep. 2016 Jun 20;6:28224. doi: 10.1038/srep28224.
Graphene photo-detectors functionalized by colloidal quantum dots (cQDs) have been demonstrated to show effective photo-detection. Although the transfer of charge carriers or energy from the cQDs to graphene is not sufficiently understood, it is clear that the mechanism and efficiency of the transfer depends on the morphology of the interface between cQDs and graphene, which is determined by the shell of the cQDs in combination with its ligands. Here, we present a study of a graphene field-effect transistor (FET), which is functionalized by long-ligand CdSe/ZnS core/shell cQDs. Time-resolved photo-luminescence from the cQDs as a function of the applied gate voltage has been investigated in order to probe transfer dynamics in this system. Thereby, a clear modification of the photo-luminescence lifetime has been observed, indicating a change of the decay channels. Furthermore, we provide responsivities under a Förster-like energy transfer model as a function of the gate voltage in support of our findings. The model shows that by applying a back-gate voltage to the photo-detector, the absorption can be tuned with respect to the photo-luminescence of the cQDs. This leads to a tunable energy transfer rate across the interface of the photo-detector, which offers an opportunity to optimize the photo-detection.
已证明由胶体量子点（cQDs）功能化的石墨烯光电探测器具有有效的光电探测能力。尽管电荷载流子或能量从cQDs转移到石墨烯的过程尚未得到充分理解，但很明显，转移的机制和效率取决于cQDs与石墨烯之间界面的形态，而这种形态是由cQDs的壳层及其配体共同决定的。在此，我们展示了一项关于由长配体CdSe/ZnS核壳cQDs功能化的石墨烯场效应晶体管（FET）的研究。为了探究该系统中的转移动力学，研究了cQDs的时间分辨光致发光随施加栅极电压的变化。由此，观察到光致发光寿命有明显改变，这表明衰减通道发生了变化。此外，我们在类Förster能量转移模型下提供了响应度随栅极电压的变化情况，以支持我们的研究结果。该模型表明，通过向光电探测器施加背栅电压，可以根据cQDs的光致发光来调节吸收。这导致光电探测器界面处的能量转移速率可调，为优化光电探测提供了机会。
