Impact of Narrowing Density of States in Semiconducting Polymers on Performance of Organic Field‐Effect Transistors

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2023-01, Vol.19 (3), p.e2205570-n/a
• Main Authors: Nakano, Kyohei, Kaji, Yumiko, Tajima, Keisuke
• Format: Article
• Language: English
• Subjects: conjugated polymers; Contact resistance; Density of states; Field effect transistors; Material properties; Nanotechnology; organic field‐effect transistors; Performance enhancement; Photoelectron Spectroscopy; photoemission spectroscopy; Polymers; Polymers - chemistry; Semiconductor devices
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.202205570

To improve the performance of organic field‐effect transistors (OFETs) employing π‐conjugated polymers, a basic understanding of the relationships between the material properties and device characteristics is crucial. Although the density of states (DOS) distribution is one of the essential material properties of semiconducting polymers, insights into how the DOS shape affects the mobility (µ), subthreshold swing (S), and contact resistance (RC) in OFETs remain lacking. In this study, by combining sensitive DOS measurements and multilayered OFET structures, it is experimentally demonstrated that narrower DOS widths in the polymer channels lead to higher µ, smaller S, and lower RC. By contrast, variation of the DOS in the bulk layer does not affect the performance. These results demonstrate a direct relationship between the polymer properties and OFET performance and highlight the importance of controlling the DOS width in π‐conjugated polymers. The density of states (DOS) of the highest occupied molecular orbital of conjugated polymers is experimentally controlled and evaluated by photoemission yield spectroscopy. Narrowing the DOS in the channel region of a field‐effect transistor increases hole mobility (µ), improves subthreshold swing (S), and reduces contact resistance (RC).