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时间:2019-10-22 11:09      发布人:何秋云      阅读:104

报告题目:Investigation of Ultrafast Charge Carrier Dynamics in Low Dimensional Energy-related Materials and Interfaces

报 告 人:王海 博士(Project leader, Molecular Spectroscopy department, Max Planck Institute for Polymer Research)

邀 请 人:苏仕健 教授/陈东成 博士

报告时间:2019年10月25日(周五)上午10:00

报告地点:北区发光材料与器件国重 502会议室

 

Abstract

In photovoltaic or photochemical cells, charge carriers are generated and transported in the photo-active materials and collected at the materials/electrode or electrolyte interfaces. Understanding and eventually controlling the generation, transport, and collection of charge carriers are therefore crucial for improving the energy conversion efficiency of devices. In this talk, I will present our recent advances in this field using terahertz (THz) spectroscopy.1-10, 13
In the first part of the talk, we will present our recent work on exploring interfacial charge transfer process in model quantum dot (QD)-sensitized oxide system. Throughout a series of systematic work1-6 (e.g. exploring QD-oxide coupling strength1, QD surface stoichiometric2, and the hot carrier3 on the charge transfer process), besides our scientific finding, we establish THz spectroscopy as a powerful tool not only for investigating the fundamental interfacial charge transfer mechanism but also for quantifying the efficiency of the process. These fundamental findings have led to a collaborative effort that set a by-then new world record efficiency for quantum dot solar cells.6

The second part of the talk will focus on the fundamentals of charge carrier dynamics in graphene and graphene nanoribbons relevant for optoelectronics and electrochemical energy conversion. Thanks to its chemical stability and exceptionally high electronic conductivities, graphene has been widely used for electrochemical energy storage, e.g., Li-battery, ionic sensors and photodetectors. In all these applications, although transport and transfer of ions and elections at varied graphene-solid, and graphene-liquid (often -electrolyte) interfaces play a critical role on the device efficiency, fundamentally the underlying mechanism and efficiency governing the processes remain largely unexplored. Employing Terahertz spectroscopy as a contact-free tool, I will present some of our ongoing projects related to track the ionic and electronic dynamics across graphene-based solid-electrolyte and solid-solid interfaces7-9, which are the key process for ionic sensing and photodetecting devices. Furthermore, recent advances in bottom-up synthesis allow atomic control of graphene nanoribbons (GNRs) with well-defined bandgap and optical properties.10-13 I will also discuss some our recent ultrafast conductivity studies on GNRs, which demonstrates the strong exciton effect in GNRs owing to the reduced charge screening effect.14

Reference

1. Wang, H. et al.Nano Lett 2013, 13, (11), 5311-5315.
2. Wang, H et al.Nano Lett 2014, 14, (10), 5780-5786.
3. Wang, H.I. et al.Nano Lett 2018, 18, (8), 5111-5115.
4. Wang, H.I. et al.ACS Nano 2017, 11, (5), 4760-4767.
5. Wang, H.I. et al.J Phys Chem Lett 2017, 8, (12), 2654-2658.
6. Zhao, K. et al.J. Am. Chem. Soc. 2015, 137, (16), 5602-5609.
7. Jia X.Y…….. Wang, H.I.*, under review.
8. Fu S. ………Wang, H.I*, to be submitted.
9. Liu Z., Wang, H.I. et al.J. Am. Chem. Soc. 2017, 139 (28), 9443–9446;
10. Chen, Z. P.; Wang, H. I.; J. Am. Chem. Soc. 2017, 139, 3635-3638;
11. Chen, Z. P.; Wang, H. I.; J. Am. Chem. Soc. 2017, 139 (28), 9483–9486;
12. J. Cai et al., Nature 2010, 466, 470-473;
13. Y Huang et al., J. Am. Chem. Soc. 2018, 140 (33), pp 10416–10420.
14. Tries, A………Wang, H.I*, to be submitted.

 

Biography

Hai Wang,Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany

Email: wanghai@mpip-mainz.mpg.de

Hai Wang studied materials science at Zhejiang University and obtained his degree in 2007. Between 2009 and 2011, he finished a joint master program in nanoscience at University of Leuven (2009-2010) in Belgium and Delft University of Technology in the Netherlands (2010-2011), supported by the Erasmus Mundus fellowship. From 2012, following his research interests in optoelectronic materials, he started his PhD at Max Planck institute for polymer research (MPIP) in Mainz with the support of a fellowship from MAINZ (graduate school of excellence, materials science in Mainz). In his PhD, Hai worked with Prof. dr. Mischa Bonn on investigating ultrafast charge transfer process at quantum dot and oxide interfaces, and graduated with Summa Cum Laude (with the highest honor) in 2016. After 1.5 year postdoc training in the group of Prof. dr. Mathias Kläui at Mainz university, Hai started his group “Nano-optoelectronic materials” in the Molecular Spectroscopy department at MPIP from August of 2017.