Issue 43, 2020

Fermi level pinned molecular donor/acceptor junctions: reduction of induced carrier density by interfacial charge transfer complexes

Abstract

Increased hole density in an electron donor-type organic semiconductor can be achieved by deposition of a strong acceptor-type molecular layer on top, and has been shown to enable adjusting the carrier density in organic field effect transistors (OFETs). This interfacial charge transfer is due to simultaneous Fermi level (EF) pinning of the donor's highest occupied level and the acceptor's lowest unoccupied level. Here, we investigate the electrical properties of such an EF-pinned junction formed by diindenoperylene (DIP, as donor) and hexafluoro-tetracyano-naphthoquinodimethane (F6, as acceptor) in OFETs, as well as its electronic properties by photoelectron spectroscopy and electrostatic modelling. We find that, in addition to the EF-pinning induced integer charge transfer across the interface, DIP and F6 form charge transfer complexes (CPXs) at their junction. The molecularly thin CPX interlayer acts as insulator and significantly reduces the density of carriers induced on either side of the junction, compared to a scenario without such an interlayer. CPX formation is thus unfavourable for the effectiveness of controlling carrier density at molecular donor/acceptor junctions by EF-pinning.

Graphical abstract: Fermi level pinned molecular donor/acceptor junctions: reduction of induced carrier density by interfacial charge transfer complexes

Supplementary files

Article information

Article type
Paper
Submitted
11 jun. 2020
Accepted
27 jul. 2020
First published
27 jul. 2020
This article is Open Access
Creative Commons BY license

J. Mater. Chem. C, 2020,8, 15199-15207

Fermi level pinned molecular donor/acceptor junctions: reduction of induced carrier density by interfacial charge transfer complexes

P. Beyer, E. Meister, T. Florian, A. Generalov, W. Brütting, N. Koch and A. Opitz, J. Mater. Chem. C, 2020, 8, 15199 DOI: 10.1039/D0TC02774J

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