Isoemissive Photoluminescence from a Quaternary System of Valley-Polarized, Defect-Bound Excitons and Trions in Two-Dimensional Transition Metal Dichalcogenides

Isoemissive Photoluminescence from a Quaternary System of Valley-Polarized, Defect-Bound Excitons and Trions in Two-Dimensional Transition Metal Dichalcogenides

The Journal of Physical Chemistry C

10.1021/acs.jpcc.1c00535

http://dx.doi.org/10.1021/acs.jpcc.1c00535

Zi-En Ooi, Jing Yee Chee, Swee Liang Wong, Chit Siong Lau, Kuan Eng Johnson Goh

Electronic, Optical and Magnetic Materials, Physical and Theoretical Chemistry, Surfaces, Coatings and Films, General Energy

08 June 2021

Ooi, Z.-E., Chee, J. Y., Wong, S. L., Lau, C. S., & Goh, K. E. J. (2021). Isoemissive Photoluminescence from a Quaternary System of Valley-Polarized, Defect-Bound Excitons and Trions in Two-Dimensional Transition Metal Dichalcogenides. The Journal of Physical Chemistry C, 125(23), 12721–12729. doi:10.1021/acs.jpcc.1c00535

Interest in the use of local band extrema, known as valleys, as a possible information carrier has in recent years been advanced by the isolation of 2D transition metal dichalcogenides (TMDCs). In some monolayer TMDCs, the structural inversion asymmetry leads to spin-valley locked states that present potential advantages for information storage and manipulation beyond existing charge- and spin-based semiconductor technologies. However, understanding of the role of defects on exciton recombination and valley scattering remains lacking and limits progress toward applications. Here, we report gate voltage-dependent polarized photoluminescence measurements on CVD-grown monolayer WS2 and MoS2 field-effect transistors and observe a quaternary system of valley polarized excitons and trions. Intriguingly, we find the spectra to exhibit isoemissive points, which were previously seen only as evidence of a binary system. We propose a rate model to explain the existence of isoemission in a quaternary system and find that the presence of isoemissive points imply a kinetic relationship between recombination and valley scattering. This relationship sheds light on the inverse relation seen between the polarization degree and photoluminescence intensity. Further consideration of the phenomenon also led to the identification of a possible new mechanism for charge carrier detrapping using the energy released from trion recombination.

Publisher Copyright

This research / project is supported by the A*STAR - 2D PHAROS
Grant Reference no. : 1527000016

This research / project is supported by the A*STAR - QTE
Grant Reference no. : A1685b0005

This research / project is supported by the Singapore National Research Foundation - CRP
Grant Reference no. : CRP21-2018-0094

This document is the Accepted Manuscript version of a Published Work that appeared in final form in The Journal of Physical Chemistry C, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/acs.jpcc.1c00535

https://oar.a-star.edu.sg/communities-collections/articles/17745

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Institute of Materials Research and Engineering