Improved Morphology and Performance from Surface Treatments of Naphthalenetetracarboxylic Diimide Bottom Contact Field-Effect Transistors

Abstract

We report bottom contact organic field-effect transistors (OFETs) with various surface treatments based on n-channel materials, specifically, 1,4,5,8-naphthalene-teracarboxylic diimides (NTCDIs) with three different fluorinated N-substituents, systematically studied with a particular emphasis on the interplay between the morphology of the organic semiconductor films and the electrical device properties. The morphological origins of the improvements were directly and dramatically visualized at the semiconductor-contact interface. As a result of a series of treatments, a large range of performances of bottom contact side-chain-fluorinated NTCDI OFETs (mobility from 1 x 10(-6) to 8 x 10(-2) cm(2)/(V s), on/off ratio from 1 x 10(2) to 1 x 10(5)) were obtained. The surface treatments enabled systems that had shown essentially no OFET activity without electrode modification activity to perform nearly as well as top contact devices made from the same materials. In addition, for the fresh bottom contact NTCDI device, the effect of gate bias stress on the tens-of-minutes time scale, during which the threshold voltage (V(t)) shifted and relaxed with similar time constants, was observed.

25th Anniversary Article: Recent Advances in n‐Type and Ambipolar Organic Field‐Effect Transistors

“…Compound 1h with perfluorophenyl substituents showed a low mobility of 0.025 cm 2 V −1 s −1 with bottom gate (BG) bottom contact (BC) geometry. However, much higher mobility of 0.87 cm 2 V −1 s −1 was obtained using bottom gate top contact (TC) geometry 57. Another work reported a mobility of 0.31 cm 2 V −1 s −1 when measured in ambient air using the same OSCs of 1h 58…”

Organic Semiconductors for Field-Effect Transistors

“…After 100 days in air, the average mobility of three OTFTs decreased from 0.62 to 0.12 cm 2 V −1 s −1 , but stabilized thereafter. In addition, the NDI derivatives with fluorinated phenyl groups or phenyl groupsubstituted fluorinated alkyls chain, 240i and 240j afforded the highest electron mobilities of 0.57 and 0.87 cm 2 V −1 s −1 , respectively [301,302]. The chlorinesubstituted NDIs 241a and 241b, which were reported by Oh et al, showed excellent electron mobilities of 0.86 and 1.26 cm 2 V −1 s −1 in nitrogen, respectively [298].…”

Materials for Printable, Transparent, and Low‐Voltage Transistors

“…Air‐stable n‐type TFTs with mobility values as high as 0.57 cm 2 V −1 s −1 have been demonstrated by Kevin See et al for NTCDI derivatives with multiple –F and –CF 3 substituted aliphatic/benzylic amines 30. Single or multiple CF 3 groups on a small side chain such as benzyl greatly increased air stability31–35 Sun et al reported that using aromatic thiols to modify the Au electrodes could improve morphology and performance of the NTCDI bottom‐contact TFTs 36…”