This article is on chemical doping or organic field-effect transistors using iodine solutions to enhance their performance. The article is a collaboration with the group eMolMat, led by Marta Mas-Torrent, and the Surfaces group, with Esther Barrena and Carmen Ocal. Mas-Torrent, Barrena and Ocal and three senior scientists at ICMAB, who participate in multiple research projects and activities. 

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Article

Chemical Doping of the Organic Semiconductor C8-BTBT-C8 Using an Aqueous Iodine Solution for Device Mobility Enhancement
Jinghai Li, Adara Babuji, Inés Temiño, Tommaso Salzillo, Francesco D'Amico, Raphael Pfattner, Carmen Ocal, Esther Barrena, Marta Mas-Torrent
Adv. Mater. Technol.2022, 7, 2101535
DOI: 10.1002/admt.202101535

The performance of organic field-effect transistors is still severely limited by factors such as contact resistance and charge trapping. Chemical doping is considered to be a promising key enabler for improving device performance, although there is a limited number of established doping protocols as well as a lack of understanding of the doping mechanisms.

Here, a very simple doping methodology based on exposing an organic semiconductor thin film to an aqueous iodine solution is reported. The doped devices exhibit enhanced device mobility, which becomes channel-length independent, a decreased threshold voltage and a reduction in the density of interfacial traps. The device OFF current is not altered, which is in agreement with the spectroscopic data that points out that no charge transfer processes are occurring.

Kelvin probe force microscopy characterization of the devices under operando conditions unambiguously proves that an important reduction of the contact resistance takes place after their exposition to the iodine solution, reaching almost ohmic contact