学术讲座

报告题目：Ultrafast Snapshots of Charge and Energy Dynamics in Low-Dimensional Materials Using THz Spectroscopy

报告时间：2026-08-07 10:30

报告人： 王海,助理教授

Utrecht University

报告地点：翔安校区能源材料大楼3号楼会议室3

报告摘要：

The conversion of light into electrical current underpins technologies such as photovoltaics and photodetectors. Understanding how charge carriers are generated, redistributed, and transported in the ultrafast (e.g from ps to ns time scale) is critical, as these processes determine recombination pathways, energy losses, and ultimately device performance. Gaining insight into such dynamics is therefore key to improving energy conversion efficiency. In this context, layered two-dimensional (2D) materials have emerged as promising platforms for next-generation optoelectronic devices. Since the discovery of graphene, the family of 2D materials has expanded rapidly to encompass a wide range of electronic phases, including metallic systems (e.g., graphene, MXenes), semiconductors (e.g., transition metal dichalcogenides), and insulators (e.g., hexagonal boron nitride). Their reduced dimensionality and strong many-body interactions provide an ideal setting for investigating and harnessing ultrafast charge-carrier and energy flow dynamics in nonequilibrium regimes, opening new opportunities for optoelectronic applications.

In this talk, I will first introduce the fundamentals of ultrafast terahertz (THz) spectroscopy and highlight its power as a contact-free probe of charge transport properties  and low-energy excitations in low-dimensional materials1-3. I will then present two recent studies: one exploring the ultrafast generation of free carriers in strongly excitonic systems through hot-carrier-assisted exciton dissociation4, and another investigating strong photothermal transport in 2D metallic MXenes with markedly slow thermal energy dissipation5. Together, these examples demonstrate how ultrafast THz spectroscopy provides unique insight into the nonequilibrium carrier and energy dissipation in nanoscale materials for optoelectronics.

References

1. Shuai Fu et al., Fundamentals of charge transport in two-dimensional framework materials, Nature Reviews Materials 2026, 11, 286–307.

2. Shuai Fu et al., Dimensional evolution of charge mobility and porosity in covalent organic frameworks, Nature Communications 2025 16 (1), 2219.

3. Wenhao Zheng et al., Band Transport by Large Fröhlich Polarons in MXenes, Nature Physics 2022, 18, 544-550.

4. Guanzhao Wen et al., Hot Exciton Dissociation in Graphene Nanoribbons, Nature Communications 2026, 17, 5260 (2026).

5. Wenhao Zheng et al., Photothermal effects control ultrafast charge transport in titanium carbide MXenes, Nature Communications 2026, 17, 1201.

报告人简介：

Dr. Hai Wang studied materials science at Zhejiang University and  obtained his degree in 2009.. 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, Hai Wang started his PhD at Max Planck Institute for Polymer Research (MPI-P) 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 to investigate ultrafast charge transfer processes at quantum dot and oxide interfaces, and graduated with Summa Cum Laude (with highest honors) in 2016. After spending 1 year in the group of Mathias Kläui at University of Mainz as a postdoc, Hai started his independent research group “Nano- optoelectronic materials” in the Molecular Spectroscopy department at MPI-P in 2017, and further moved to Utrecht University as an (tenured) assistant professor. Employing time-resolved, ultrafast spectroscopies (THz spectroscopy, transient absorption etc.), the central theme of Hai’s current research lies in understanding fundamental charge carrier dynamics and low-energy excitations in solid-state low-dimensional materials and interfaces, relevant for energy and optoelectronic applications.

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