Moderate doping leads to high performance of semiconductor/insulator polymer blend transistors

• Published in: Nature communications Vol. 4; no. 1; p. 1588
• Main Authors: Lu, Guanghao, Blakesley, James, Himmelberger, Scott, Pingel, Patrick, Frisch, Johannes, Lieberwirth, Ingo, Salzmann, Ingo, Oehzelt, Martin, Di Pietro, Riccardo, Salleo, Alberto, Koch, Norbert, Neher, Dieter
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 12.03.2013; Nature Publishing Group
• Subjects: 639/301/119/995; 639/638/298/923/1028; Humanities and Social Sciences; multidisciplinary; Polymer blends; Polymers; R&D; Research & development; Science; Science (multidisciplinary); Spatial distribution; Transistors; United States > US; Berlin Germany; Massachusetts; Germany
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms2587

Polymer transistors are being intensively developed for next-generation flexible electronics. Blends comprising a small amount of semiconducting polymer mixed into an insulating polymer matrix have simultaneously shown superior performance and environmental stability in organic field-effect transistors compared with the neat semiconductor. Here we show that such blends actually perform very poorly in the undoped state, and that mobility and on/off ratio are improved dramatically upon moderate doping. Structural investigations show that these blend layers feature nanometre-scale semiconductor domains and a vertical composition gradient. This particular morphology enables a quasi three-dimensional spatial distribution of semiconductor pathways within the insulating matrix, in which charge accumulation and depletion via a gate bias is substantially different from neat semiconductor, and where high on-current and low off-current are simultaneously realized in the stable doped state. Adding only 5 wt% of a semiconducting polymer to a polystyrene matrix, we realized an environmentally stable inverter with gain up to 60. Blends of different polymer compounds are widely used for organic field-effect transistors. Here, Neher and colleagues show that moderate carrier doping is important to achieve maximum performance in blends of insulating and semiconducting polymers.