Issue 3, 2024

Enthalpy-uphill exciton dissociation in organic/2D heterostructures promotes free carrier generation

Abstract

Despite the large binding energy of charge transfer (CT) excitons in type-II organic/2D heterostructures, it has been demonstrated that free carriers can be generated from CT excitons with a long lifetime. Using a model fluorinated zine phthalocyanine (F8ZnPc)/monolayer-WS2 interface, we find that CT excitons can dissociate spontaneously into free carriers despite it being an enthalpy-uphill process. Specifically, it is observed that CT excitons can gain an energy of 250 meV in 50 ps and dissociate into free carriers without any applied electric field. This observation is surprising because excited electrons typically lose energy to the environment and relax to lower energy states. We hypothesize that this abnormal enthalpy-uphill CT exciton dissociation process is driven by entropy gain. Kinetically, the entropic driving force can also reduce the rate for the reverse process – the conversion of free electron–hole pairs back to CT excitons. Hence, this mechanism can potentially explain the very long carrier lifetime observed in organic/2D heterostructures.

Graphical abstract: Enthalpy-uphill exciton dissociation in organic/2D heterostructures promotes free carrier generation

  • This article is part of the themed collection: #MyFirstMH

Supplementary files

Article information

Article type
Communication
Submitted
22 9 2023
Accepted
20 11 2023
First published
20 11 2023

Mater. Horiz., 2024,11, 813-821

Enthalpy-uphill exciton dissociation in organic/2D heterostructures promotes free carrier generation

F. Rudayni, K. Rijal, N. Fuller and W. Chan, Mater. Horiz., 2024, 11, 813 DOI: 10.1039/D3MH01522J

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements