Enhanced Polymer Thin Film Transistor Performance by Carefully Controlling the Solution Self‐Assembly and Film Alignment with Slot Die Coating

Abstract

Polymer‐based organic semiconductors inherently facilitate solution processing and have the mechanical robustness necessary for printable and large area applications. In order to achieve large area solution‐processed high‐performance polymer based devices, controlling the crystallization and self‐assembly behavior of the polymer thin films through solution processing method is desirable. Here, well controlled diketopyrrolopyrrole‐thieno[3,2‐b]thiophene copolymer (DPPT‐TT) thin films are developed using slot die coating controlled self‐assembly. The thin film morphologies and microstructure are investigated in details. This well‐defined morphology is rationalized in terms of the strong intermolecular interactions. The organic thin film transistors (OTFTs) with these controlled thin films are fabricated and exhibited charge carrier mobilities of 4.6–7.2 cm2 V−1 s−1 for the slot die coating controlled devices when measured in ambient air and up to 8.9–10.2 cm2 V−1 s−1 when measured in nitrogen. When applying native grown AlO x as gate dielectric, the OTFT achieves a mobility of 2.0 cm2 V−1 s−1 at the operating voltage ≤−3 V.

Directional Solution Coating by the Chinese Brush: A Facile Approach to Improving Molecular Alignment for High‐Performance Polymer TFTs

“…Moreover, the higher planar DPP‐based conjugated backbones exhibit better intrachain and interchain charge transport . Besides the delicate polymer design, directly aligning the D–A conjugated backbones toward the source and drain electrodes is an appealing strategy for improving electrical performance . Therefore, developing a facile and efficient approach to realize the oriented polymer thin film is in a demand.…”

“…Solution‐coating techniques capable of fabricating oriented polymer thin films, such as brush‐painting, solution shearing, slot die coating,[8a] bar coating,[8b] dip coating,[8c] off‐center spin coating, and directional drying have been vigorously developed. Using these techniques, the conjugated polymer backbone alignment is proceeded under the directional stress (the directional shearing force, the centrifugal force, and the gradient evaporation force), which is aroused by the directional fluid flow, with controlling the durations for self‐assembly of polymer chains.…”

Controlling aggregation and crystallization of solution processed diketopyrrolopyrrole based polymer for high performance thin film transistors by pre-metered slot die coating process

“…The estimated pep stacking distance was 0.37 nm. This is similar to most of DPP based conjugated polymers [17,38].…”

“…Among these methods, slot die coating has been proved to be a simplistic and manufacturable approach to fabricate large area high performance field effect transistors. Most importantly, it was found that this method is not only suitable for small molecule system like TIPS-pentacene [24], but also useful for polymer systems like diketopyrrolopyrrole-thieno[3,2-b]thiophene copolymer (PDPPT-TT) [17]. This technique saves raw materials and controls film uniformity reliably, accurately, and reproducibly.…”

Organic Field-Effect Transistor: Device Physics, Materials, and Process

“…Moreover, the device exhibited excellent shelf life and operating stabilities under ambient conditions. Finally, exceptionally high-gain inverters and functional ring oscillator devices on flexible substrates have been demonstrated [45,46].…”