SCIENTIFIC HIGHLIGHTS RL4, Reviews

Printed organic field-effect transistors using inks based on organic semiconducting molecules blended with insulating polymers

The use of inks based on organic semiconducting molecules blended with insulating polymers results in large area crystalline films exhibiting high field-effect mobilities.

The development of low‐cost organic electronics entails the processing of organic semiconductors employing solution‐based techniques in order to be able to print them at low temperature and on flexible substrates. Small conjugated semiconducting molecules can form highly ordered crystalline structures that give rise to high charge carrier mobilities. However, due to the low viscosity of their solutions, the preparation of large‐area uniform and reproducible films of these materials employing printing techniques can be very challenging. To circumvent this, a promising route is the use of blends of the organic semiconductors with insulating binding polymers. The resulting formulations are more viscous, facilitating the preparation of films covering large areas without facing dewetting issues and with high reproducibility.

Additionally, this approach typically gives rise to films with an enhanced crystallinity due to the vertical phase separation that takes place during the deposition, which works as a crystallisation process. Therefore, when the films are implemented in organic field‐effect transistor (OFETs), the devices exhibit a significantly improved performance in terms of mobility and stability. In this review paper, we describe the recent progress in the fabrication of OFETs based on inks of small semiconducting molecules with insulating polymers. Particular emphasis is placed on the morphology and structural characteristics of the films since they play a major role in determining the final electrical properties. 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 organic semiconductors in real‐world applications.

Organic semiconductor/polymer blend films for organic field-effect transistors
Sergi Riera-Galindo, Francesca Leonardi, Raphael Pfattner, Marta Mas-Torrent
Adv. Mater. Technol. 1900104, 2019
DOI: 10.1002/admt.201900104

Figure: Organic field-effect transistor based on a an organic semiconducting molecule/insulating polymer blended film.

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