Contact Resistance in Ambipolar Organic Field-Effect Transistors Measured by Confocal Photoluminescence Electro-Modulation Microscopy
- Although it is theoretically expected that all organic semiconductors support ambipolar charge transport, most organic transistors either transport holes or electrons effectively. Single-layer ambipolar organic field-effect transistors enable the investigation of different mechanisms in hole and electron transport in a single device since the device architecture provides a controllable planar pn-junction within the transistor channel. However, a direct comparison of the injection barriers and of the channel conductivities between electrons and holes within the same device cannot be measured by standard electrical characterization. This article introduces a novel approach for determining threshold gate voltages for the onset of the ambipolar regime from the position of the pn-junction observed by photoluminescence electromodulation (PLEM) microscopy. Indeed, the threshold gate voltage in the ambipolar bias regime considers a vanishing channel length, thus correlating the contact resistance. PLEM microscopy is a valuable tool toAlthough it is theoretically expected that all organic semiconductors support ambipolar charge transport, most organic transistors either transport holes or electrons effectively. Single-layer ambipolar organic field-effect transistors enable the investigation of different mechanisms in hole and electron transport in a single device since the device architecture provides a controllable planar pn-junction within the transistor channel. However, a direct comparison of the injection barriers and of the channel conductivities between electrons and holes within the same device cannot be measured by standard electrical characterization. This article introduces a novel approach for determining threshold gate voltages for the onset of the ambipolar regime from the position of the pn-junction observed by photoluminescence electromodulation (PLEM) microscopy. Indeed, the threshold gate voltage in the ambipolar bias regime considers a vanishing channel length, thus correlating the contact resistance. PLEM microscopy is a valuable tool to directly compare the contact and channel resistances for both carrier types in the same device. The reported results demonstrate that designing the metal/organic semiconductor interfaces by aligning the bulk metal Fermi levels to the highest occupied molecular orbital or lowest unoccupied molecular orbital levels of the organic semiconductors is a too simplistic approach for optimizing the charge injection process in organic field-effect devices.…
Verfasserangaben: | Wouter-Willem Adriaan KoopmanORCiDGND, Marco NataliORCiD, Cristian Bettini, Manuela Melucci, Michele MucciniORCiD, Stefano ToffaninORCiD |
---|---|
DOI: | https://doi.org/10.1021/acsami.8b05518 |
ISSN: | 1944-8244 |
Pubmed ID: | https://pubmed.ncbi.nlm.nih.gov/30230308 |
Titel des übergeordneten Werks (Englisch): | ACS applied materials & interfaces |
Verlag: | American Chemical Society |
Verlagsort: | Washington |
Publikationstyp: | Wissenschaftlicher Artikel |
Sprache: | Englisch |
Datum der Erstveröffentlichung: | 17.10.2018 |
Erscheinungsjahr: | 2018 |
Datum der Freischaltung: | 03.08.2021 |
Freies Schlagwort / Tag: | contact resistance; electro-modulation microscopy; organic field-effect transistors; photoluminescence; threshold voltages |
Band: | 10 |
Ausgabe: | 41 |
Seitenanzahl: | 9 |
Erste Seite: | 35411 |
Letzte Seite: | 35419 |
Organisationseinheiten: | Mathematisch-Naturwissenschaftliche Fakultät / Institut für Physik und Astronomie |
DDC-Klassifikation: | 5 Naturwissenschaften und Mathematik / 53 Physik / 530 Physik |
Peer Review: | Referiert |
Publikationsweg: | Open Access / Bronze Open-Access |