Organic semiconductors have received lots of attentions in recent years, because of their promising applications in the low-cost production of flexible and light-weight electronics, such as wearable devices. Charge carrier mobility is a crucial parameter for the organic semiconductors. Development of organic semiconducting devices with high mobility and high ON/OFF ratio is very important.

Research group led by Prof. ZHANG Deqing at Institute of Chemistry, the Chinese Academy of Sciences (ICCAS) has make progress in enhancing the charge carrier mobility of conjugated polymer through a new and simple approach, by collaborating with Prof. Henning Sirringhaus at Cavendish Laboratory, University of Cambridge.

By incorporating an ionic additive, tetramethyl ammonium iodide (NMe₄I), the charge carrier mobility of conjugated polymer [poly-[2,5-bis(2-octyldodecyl)-3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H) -dionel-alt-thieno[3,2-b]thiophene, DPPTTT] can be remarkably enhanced without any extra treatments. The resulting thin films exhibit a very high hole mobility up to 26.2 cm²V^-1s^-1, which is higher by a factor of 24 than that without the ionic additive polymer devices. In addition, the devices still maintain high ON/OFF ratios of 10⁶-10⁷. Based on GIWAXS and AFM characterizations as well as theoretical calculations, the enhancement of charge mobility can be attributed primarily to an inhibition of the torsional motion of the alkyl side chains by the presence of the ionic species, which facilitates a more ordered lamellar packing of the alkyl side chains and inter-chain π-π stackings.

Their work entitled “Remarkable enhancement of charge carrier mobility of conjugated polymer field-effect transistors upon incorporating an ionic additive” has been published in Science Advances (2016, 2, e1600076).

This research was financially supported by CAS, NSFC and 973 Program of China.

Illustration of enhancing the mobility of conjugated polymer (DPPTTT) by incorporating an ionic additive. (Image by LIU Zitong)

Contact:

Prof. ZHANG Deqing

CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences

Email: dqzhang@iccas.ac.cn