All About the Interface: Do Residual Contaminants at A High‐Quality h‐BN Monolayer Perylene Diimide Interface Cause Charge Trapping?. Issue 10 (29th January 2022)

• Record Type: Journal Article
• Authors: Renn, Lukas; Walter, Lisa S.; Watanabe, Kenji; Taniguchi, Takashi; Weitz, R. Thomas
• Is Part Of: Advanced materials interfaces. Volume 9:Issue 10(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-01-29
• Subjects: charge transport -- field‐effect transistor -- interface -- organic semiconductor -- van‐der‐Waals; Materials science -- Periodicals; 620.11
• DOI: 10.1002/admi.202101701
• Languages: English
• ISSNs: 2196-7350

Abstract

Abstract: Intrinsic charge transport in molecularly thin organic semiconducting crystals is critically sensitive to the quality of the interfaces required to perform the electrical measurements. Most prominent are the dielectric–semiconductor and semiconductor–metal interface. While impacts from the latter on charge transport can be extracted by four‐terminal measurements, the impact of the dielectric interface can only be minimized, typically by utilizing inert dielectrics. Here, it is shown that charge transport in organic field‐effect transistors based on the n ‐type small molecule N, N ′‐di((S)‐1‐methylpentyl)‐1, 7(6)‐dicyano‐perylene‐3, 4:9, 10‐bis(dicarboximide) (PDI1MPCN2) can be improved up to one order of magnitude by using hexagonal boron nitride (h‐BN) as dielectric, compared to a standard SiO2 substrate. Using temperature‐dependent electrical measurements, the charge‐transport properties of devices are systematically analyzed, and high four‐terminal mobilities of up to 5.0 cm 2 V −1 s −1 are obtained. The high mobility likely stems from decreased charge‐carrier trapping at the semiconductor‐dielectric interface due to the smooth surface of the inert h‐BN. Nevertheless, the temperature dependencies of the mobility, threshold voltage, and interface‐state trap density suggest that charge‐carrier trapping at the dielectric‐semiconductor interface still exists. By comparing the data to transport studies performed on thin air‐gapped organic films, it is concluded that an interfacial layer (likely water or solvent residues) between h‐BN and the monolayer PDI1MPCN2 causes charge trapping. Abstract : Organic transistors consisting of a monolayer‐thin perylene‐diimide n‐channel semiconductor show signs of interfacial charge trapping even though a trap‐free h‐BN dielectric is used. These observations suggest that even at this nominally perfect semiconductor–dielectric interface, interfacial contaminants are present, potentially in the form of water and/or solvent residues.