Ultrafast Charge Separation in Bilayer WS2/Graphene Heterostructure Revealed by Time- and Angle-Resolved Photoemission Spectroscopy

Frontiers in Physics

Stiven Forti¹  Camilla Coletti²  Antonio Rossi³  Filippo Fabbri⁴  Yu Zhang⁵  Richard T. Chapman⁵  Emma Springate⁵  Paulina Ewa Majchrzak⁶  Cephise Cacho⁷  Isabella Gierz⁸  Sven Aeschlimann⁹  Razvan Krause⁹  Mariana Chávez-Cervantes^1,10 

[1] Center for Nanotechnology Innovation at IIT@NEST, Istituto Italiano di Tecnologia, Pisa, Italy;Center for Nanotechnology Innovation at IIT@NEST, Istituto Italiano di Tecnologia, Pisa, Italy;Graphene Labs, Istituto Italiano di Tecnologia, Genova, Italy;Center for Nanotechnology Innovation at IIT@NEST, Istituto Italiano di Tecnologia, Pisa, Italy;National Enterprise for nanoScience and nanoTechnology (NEST), Istituto Nanoscienze, Consiglio Nazionale delle Ricerche (CNR) and Scuola Normale Superiore, Pisa, Italy;Center for Nanotechnology Innovation at IIT@NEST, Istituto Italiano di Tecnologia, Pisa, Italy;National Enterprise for nanoScience and nanoTechnology (NEST), Istituto Nanoscienze, Consiglio Nazionale delle Ricerche (CNR) and Scuola Normale Superiore, Pisa, Italy;Graphene Labs, Istituto Italiano di Tecnologia, Genova, Italy;Central Laser Facility, Science and Technology Facilities Council (STFC) Rutherford Appleton Laboratory, Didcot, United Kingdom;Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark;Diamond Light Source, Harwell Science and Innovation Campus, Didcot, United Kingdom;Institute for Experimental and Applied Physics, University of Regensburg, Regensburg, Germany;Institute for Experimental and Applied Physics, University of Regensburg, Regensburg, Germany;Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, Hamburg, Germany;Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, Hamburg, Germany;

关键词: TMD;    graphene;    van der Waals heterostructures;    tr-ARPES;    ultrafast charge transfer;    photovoltaics;   

DOI  :  10.3389/fphy.2021.668149

来源: Frontiers

【 摘 要 】

Efficient light harvesting devices need to combine strong absorption in the visible spectral range with efficient ultrafast charge separation. These features commonly occur in novel ultimately thin van der Waals heterostructures with type II band alignment. Recently, ultrafast charge separation was also observed in monolayer WS2/graphene heterostructures with type I band alignment. Here we use time- and angle-resolved photoemission spectroscopy to show that ultrafast charge separation also occurs at the interface between bilayer WS2 and graphene indicating that the indirect band gap of bilayer WS2 does not affect the charge transfer to the graphene layer. The microscopic insights gained in the present study will turn out to be useful for the design of novel optoelectronic devices.

【 授权许可】

CC BY