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Charge transfer processes and space charge accumulation phenomena are fundamental topics concerning the technological applications of organic heterointerfaces. The possibility to achieve localized regions with enhanced charge density is, indeed, a powerful strategy to improve the performances of a vast plethora of electronic devices such as light emitting diodes, photodetectors and field-effect transistors. However, because of the complex structures of many organic compounds and the diversity of electronic interactions ruled by specific morphological features, the interfacial energy landscape of any combination of materials is needed to be carefully investigated. In this work, we provide a detailed analysis of the surface potential landscape of P3HT/PDIF-CN2 donor/acceptor organic heterointerfaces. The electrical characterization, relying on the field-effect transistor configuration, outlined that the presence of a PDIF-CN2 overlayer induces a semiconductor-to-conductor transition into spin-coated P3HT OFETs. The mutual doping of the two organic materials was analyzed by Scanning Kelvin Probe Force Microscopy (SKPFM) as a function of the PDIF-CN2 coverage and nominal thickness, with the results clearly pointing at the occurrence of charge transfer phenomena between the two materials. The related band bending at the interface brings to the formation of a hole rich area within the P3HT layer and an electron rich area within the PDIF-CN2 layer. The related thickness and charge density have been estimated in 15 nm and ≈1018cm-3, respectively. Significantly, by tuning the PDIF-CN2 overlayer coverage, the P3HT work function can be tuned within 1 eV, opening an interesting perspective for the achievement of organic optoelectronic devices with improved functionalities.

Contact resistance effects in n-type organic field-effect transistors (OFETs) based on perylene-diimide thin films and monolayer CVD graphene electrodes have been investigated by using Scanning Kelvin Probe Force Microscopy (SKPFM). SKPFM voltage profiles were acquired as a function of the applied drain–source (Vds) and gate–source (Vgs) voltages and in the temperature range between 300 and 360 K. The results were compared with those obtained for hybrid devices bearing contemporarily a gold and a graphene electrode, in order to highlight the specific behaviors of the graphene/organic and gold/organic interfaces. Despite the fact that overall electrical performances of devices based on gold and graphene contacts are fully comparable, the SKPFM analysis demonstrates unambiguously that the physical mechanisms driving the charge injection and extraction phenomena are distinctive based on the electrode type. While for OFETs with gold electrodes, the RC effect is mainly ascribable to the degraded quality of the charge transport in the semiconducting film regions close to the electrodes, for graphene-based devices, it is related to the presence of a Schottky-like barrier at the injecting electrode.

Correction for ‘Space-charge accumulation and band bending at conductive P3HT/PDIF-CN2 interfaces investigated by scanning-Kelvin probe microscopy’ by Federico Chianese et al., J. Mater. Chem. C, 2021, DOI: 10.1039/d1tc04840f.