Modulating Organic Transistor Performance by Optimizing Organic-Organic Interface Charge Transfer

Abstract

Organic heterojunctions have demonstrated significant potential in modulating the properties and performance of organic electronic devices through interfacial charge effects. However, these effects are critically dependent on the electronic structure and film morphology, which can lead to unpredictable variations in device performance. In this study, we systematically investigated the interfacial charge transfer between two thiophene derivatives and achieved optimized organic field-effect transistor (OFET) performance through interface engineering. The heterojunction is constructed via 2,7-dihexyl-dithieno[2,3-d;2′,3′-d′]benzo[1,2-b;4,5-b′]dithiophene (DTBDT-C6) and dicyanovinylterthiophene (DCV3T), with density functional theory (DFT) calculations revealing distinct HOMO-LUMO distributions that facilitate charge transfer at the interface. This is further confirmed through in situ photoluminescence spectroscopy, X-ray photoelectron spectroscopy (XPS) and Kelvin probe force microscopy (KPFM). The OFET performance exhibits a pronounced thickness dependence, where both the off-state current and charge mobility initially increase but subsequently decrease with increasing DCV3T thickness. This behavior is attributed to the competing effects of enhanced conductivity and thickness-dependent injection barriers at the interface. By spatially confining DCV3T to an optimal thickness at the electrodesemiconductor interface together with dielectric surface modification, we achieved a balanced performance with a super on/off current ratio of 10⁷ and a high mobility over 1 cm²·V⁻¹·s⁻¹. These results underscore the importance of heterojunction engineering in advancing device operation.

Keywords

Organic field-effect transistor (OFET) / Organic heterojunction / Interface charge transfer / Spatially confining

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Jilin University, The Editorial Department of Chemical Research in Chinese Universities and Springer-Verlag GmbH