Abstract
AbstractThe development of low‐cost printed organic electronics entails the processing of active organic semiconductors (OSCs) through solution‐based techniques. However, the preparation of large‐area uniform and reproducible films based on OSC inks can be very challenging due to the low viscosity of their solutions, which causes dewetting problems, the low stability of OSC polymer solutions, or the difficulty in achieving appropriate crystal order. To circumvent this, a promising route is the use of blends of OSCs and insulating binding polymers. This approach typically gives rise to films with an enhanced crystallinity and organic field‐effect transistors (OFETs) with significantly improved device performance. Recent progress in the fabrication of OFETs based on OSC/binding polymer inks is reviewed, highlighting the main morphological and structural features that play a major role in determining the final electrical properties and some future perspectives. Undoubtedly, the use of these types of blends results in more reliable and reproducible devices that can be fabricated on large areas and at low cost and, thus, this methodology brings great expectations for the implementation of OSCs in real‐world applications.
Highlights
Over the last two decades the field of organic electronics has witnessed a massive increase in the performance of organic field-effect transistors (OFETs) thanks to the intense work devoted, which was motivated by the potential of these devices for low-cost and flexible applications
Another challenge lies on the preparation of large area uniform and reproducible films based on organic semiconductors (OSCs) inks
The improved crystallization was attributed to the viscosity gradient at the meniscus during dip‐coating imparted by the polymer that facilitates the mass transport, and to the fact that the polymer binder solidified at the bottom layer reducing the nucleation barrier height of the small molecule OSCs
Summary
Over the last two decades the field of organic electronics has witnessed a massive increase in the performance of organic field-effect transistors (OFETs) thanks to the intense work devoted, which was motivated by the potential of these devices for low-cost and flexible applications. Small-molecule OSCs tend to form more ordered structures but the preparation of large area uniform films is extremely challenging These materials were first mainly studied by evaporating them at ultra-high vacuum or by the controlled growth of single crystals. The addition of a small fraction of PMMA as binding polymer has been fundamental to improve the crystallisation of the thiophene derivatives α,ω‐dihexylquaterthiophene (DH4T) and diketopyrrolopyrrole‐sexithiophene (DPP6T) processed by dip-coating.[44] The improved crystallization was attributed to the viscosity gradient at the meniscus during dip‐coating imparted by the polymer that facilitates the mass transport, and to the fact that the polymer binder solidified at the bottom layer reducing the nucleation barrier height of the small molecule OSCs. The use of blends has permitted the preparation of films of promising materials that, display poor coating properties or limited solubility. The resulting OFETs exhibited almost four times higher mobility than the neat QBS semiconductor, giving hole/electron mobilities of 0.08/0.02 cm2V1s-1
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