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.^[1-4] However, even non-functional molecules can be served for the implementation of molecular diode with employing appropriate energy band alignment in heterostructure molecular 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.^[5] A two-dimensional (2D) semiconductor (MoS₂ and WSe₂) was used as a rectifying designer at the alkyl or conjugated molecule/Au interface. From the adjustment of band alignment at molecules/2D semiconductor interface that can activate different transport pathways depending on the voltage polarity, the rectifying characteristics can be implemented and controlled. To demonstrate the molecular tunneling in positive bias region and Schottky emission in negative bias region, we performed temperature-dependent measurements of the solid-state devices composed of Gr/N_L-MoS₂/OPT2/Au junctions. 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 2D 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.

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[5] Shin, J. et al. Tunable rectification in a molecular heterojunction with two-dimensional semiconductors. Nat. Commun. 11, 1412 (2020).