Abstract
Thin film field-effect transistors based on binary blends of poly(3-hexylthiophene) (P3HT) and two perylene diimide (PDI) derivatives with different alkyl substituents have been investigated in terms of device performance, microstructure and molecular organization on the surface. For the same blend ratios the PDIs phase separate differently due to solubility variation. Blends with a horizontal phase separation between the donor and acceptor show ambipolar behavior due to well defined homogenous pathways for both charge carriers. In this layer arrangement the polymer is located near the dielectric interface, while the PDI molecules crystallize on top of the film. Interestingly, the electron mobility is improved by a few orders of magnitude in comparison to the pure acceptor. This increase is attributed to the altered microstructure of PDI in the blends. Layers in which the PDI crystals are embedded within the polymer matrix and are not interconnected with each other lead only to hole transport in the transistor. For one blend ratio, the hole mobility improves by one order of magnitude compared to pure P3HT as a result of the reorganization of the polymer in the blend layer. This study provides new insights into the role of microstructure and molecular organization in the charge carrier transport in heterojunction field-effect transistors for the development of high-performance future devices.
Highlights
Organic eld-effect transistors (FETs) based on solution processable conjugated polymers are technologically attractive as active components in cheap and exible electronic devices such as radio frequency identi cation (RF-ID) tags and active matrix of exible displays.[1]
Compound perylene diimide (PDI)-2 was speci cally designed to increase the solubility by additional bulky alkyl side chains in comparison to PDI-1
PDI-1 served as the starting material for the synthesis of PDI-2, which carries additional bulky alkyl-substituents at the 2, 5, 8, and 11-position of the PDI core
Summary
Organic eld-effect transistors (FETs) based on solution processable conjugated polymers are technologically attractive as active components in cheap and exible electronic devices such as radio frequency identi cation (RF-ID) tags and active matrix of exible displays.[1]. The domains are obviously separated from each other by distinct grain boundaries which are known to limit the charge carrier transport in thin layers.[21] Equatorial re ections at qx,y 1⁄4 1.85 AÀ1 in the GIWAXS pattern for PDI-1 are assigned to the p-stacking distance of 3.4 Aand indicate an edge-on arrangement of the molecules on the surface (Fig. 2b and S1†).
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