Decoding the Vertical Phase Separation and Its Impact on C8-BTBT/PS Transistor Properties
Disentangling the details of the vertical distribution of the small semiconductor molecules blended with polystyrene (PS) and the contacts properties are issues of fundamental value for designing strategies to optimize small molecule/polymer blend organic transistors. These questions are addressed h...
| Autores: | , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión aceptada para publicación |
| Fecha de publicación: | 2018 |
| País: | España |
| Institución: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/161898 |
| Acceso en línea: | http://hdl.handle.net/10261/161898 |
| Access Level: | acceso abierto |
| Palabra clave: | Organic semiconductors Friction anisotropy AFM OFETs C8-BTBT |
| Sumario: | Disentangling the details of the vertical distribution of the small semiconductor molecules blended with polystyrene (PS) and the contacts properties are issues of fundamental value for designing strategies to optimize small molecule/polymer blend organic transistors. These questions are addressed here for ultra-thin blends of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) and PS processed by a solution-shearing technique using three different blend composition ratios. We show that friction force microscopy (FFM) allows the determination of the lateral and vertical distribution of the two materials at the nanoscale. Our results demonstrate a three layer stratification of the blend: a film of C8-BTBT of few molecular layers with crystalline order sandwiched between a PS-rich layer at the bottom (a few nm thick) acting as passivating dielectric layer and a PS-rich skin layer on the top (~1nm) conferring stability to the devices. Kelvin probe force microscopy (KPFM) measurements performed in operating organic field-effect transistors (OFETs) reveal that the devices are strongly contact limited and suggest contact doping as route for device optimization. By excluding the effect of the contacts, field-effect mobility values in the channel as high as 10 cm2V-1s-1 are obtained. Our findings, obtained via a combination of FFM and KPFM, provide a satisfactory explanation of the different electrical performance of the OFETs as a function of the blend composition ratio and by doping the contacts. |
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