All About the Interface: Do Residual Contaminants at A High‐Quality h‐BN Monolayer Perylene Diimide Interface Cause Charge Trapping?

Intrinsic charge transport in molecularly thin organic semiconducting crystals is critically sensitive to the quality of interfaces required perform electrical measurements. Most prominent are dielectric–semiconductor and semiconductor–metal interface. While impacts from latter on can be extracted by four-terminal measurements, impact dielectric interface only minimized, typically utilizing inert dielectrics. Here, it shown that field-effect transistors based n-type small molecule N, N′-di((S)-1-methylpentyl)-1,7(6)-dicyano-perylene-3,4:9,10-bis(dicarboximide) (PDI1MPCN2) improved up one order magnitude using hexagonal boron nitride (h-BN) as dielectric, compared a standard SiO2 substrate. Using temperature-dependent charge-transport properties devices systematically analyzed, high mobilities 5.0 cm2 V−1 s−1 obtained. The mobility likely stems decreased charge-carrier trapping at semiconductor-dielectric due smooth surface h-BN. Nevertheless, temperature dependencies mobility, threshold voltage, interface-state trap density suggest dielectric-semiconductor still exists. By comparing data studies performed air-gapped films, concluded an interfacial layer (likely water or solvent residues) between h-BN monolayer PDI1MPCN2 causes trapping.