Tunable rectification in a molecular heterojunction with two-dimensional semiconductors

Jaeho Shin,Gunuk Wang,Chul-Ho Lee,Seunghoon Yang,Yeonsik Jang,Tae-Wook Kim,Jung Sun Eo,Takhee Lee

doi:10.1038/s41467-020-15144-9

Jaeho Shin, Gunuk Wang + Show 6 more

Open Access

https://doi.org/10.1038/s41467-020-15144-9

Copy DOI

Abstract

Until now, a specifically designed functional molecular species has been recognized as an absolute necessity for realizing the diode’s behavior in molecular electronic junctions. Here, we suggest a facile approach for the implementation of a tailored diode in a molecular junction based on non-functionalized alkyl and conjugated molecular monolayers. A two-dimensional semiconductor (MoS2 and WSe2) is used as a rectifying designer at the alkyl or conjugated molecule/Au interface. From the adjustment of band alignment at molecules/two-dimensional semiconductor interface that can activate different transport pathways depending on the voltage polarity, the rectifying characteristics can be implemented and controlled. The rectification ratio could be widely tuned from 1.24 to 1.83 × 104 by changing the molecular species and type and the number of layers of the two-dimensional semiconductors in the heterostructure molecular junction. Our work sets a design rule for implementing tailored-diode function in a molecular heterojunction structure with non-functionalized molecular systems.

Highlights

Until now, a designed functional molecular species has been recognized as an absolute necessity for realizing the diode’s behavior in molecular electronic junctions
The D-σ-A type molecules have been widely used for a diode component, where the highest-occupied molecular orbital (HOMO) of the donor and the lowest-unoccupied molecular orbital (LUMO) of the acceptor are closely aligned to the Fermi level of electrodes, i.e., the frontier orbital level of each molecular unit is asymmetrically positioned with respect to the electrodes[9,10]
In the case of the ferrocenyl molecules that composed of long alkyl chain and ferrocenyl termini unit, they can exhibit the rectification characteristic because the charge transport pathways are mainly determined by the relative HOMO level of the ferrocenyl unit according to voltage polarities[11,12]

Summary

Introduction

A designed functional molecular species has been recognized as an absolute necessity for realizing the diode’s behavior in molecular electronic junctions. To understand the rectifying mechanism and the difference in the RR for the OPT2/1L-MoS2 and OPT2/1L-WSe2 junctions, we establish different interfacial energy band alignments for both heterojunctions, corresponding to the different applied voltages (V = 0, 1.0, and −1.0 V) (Fig. 2d and Supplementary Fig. 5).

Results

Conclusion