主讲人：王海，荷兰乌得勒支大学&德国马普聚合物研究所
时 间：2026年4月1日 9:00
地 点：物电学院A栋414
联系人：余晓青
讲座摘要：The conversion of light into electrical current underpins technologies such as photovoltaics and photodetectors, but its efficiency is often fundamentally governed by ultrafast, nonequilibrium charge carrier dynamics on picosecond (ps) timescales following photoexcitation. Understanding how charge carriers are generated, redistributed, and transported during these early stages 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 building blocks for next-generation electronic and optoelectronic devices. Since the discovery of graphene, the family of 2D materials has rapidly expanded to include a diverse range of electronic phases, spanning metallic systems (e.g., graphene), semiconducting materials (e.g., transition metal dichalcogenides), and insulating compounds (e.g., hexagonal boron nitride). Their reduced dimensionality and unique electronic structures make them particularly well-suited for exploring and exploiting ultrafast charge carrier dynamics in nonequilibrium regimes towards novel optoelectronics. In this talk, I will first provide some basics on ultrafast THz spectroscopy and demonstrate its strength in characterization of electrical transport properties of charge carriers and low-energy excitations in solids in a contact-free manner for low-dimensional materials. I will then discuss some recent work from us related to the ultrafast “birth” and transport effects of charge carriers following photoexcitation by photoconductivity studies, with a particular focus on the role of many-body interactions (carrier-carrier, carrier-phonon interactions) in dictating the process of hot carrier relaxation, transport and transfer, and lattice heating and cooling dynamics.
主讲人简介：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 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 oxide interfaces, and graduated with the highest honor 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 a tenured assistant professor in 2023. 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.
