| 研究実績の概要 |
The microspacing in-air sublimation (MAS) method was successfully used to grow and evaluate single crystal (SCs) of various organic semiconductor (OSC) materials including rubrene, pentacene, DNTT, and novel OSCs developed in our group. The growth of SCs via the liquid phase (essential for the proposed research) was also realized, but only for rubrene. For most OSCs useful for organic field-effect transistors (OFETs) applications, nucleation turned out to be too rapid to form droplets during MAS. Patterned MAS was performed using octadecyltrichlorosilane/bare SiO2/Si substrates (prepared by ultraviolet light exposure through a photomask). As expected, much larger droplets of rubrene formed on bare areas resulting in much larger SCs. Unfortunately, the resulting SCs were mostly of block-type irregular shape which made their application in OFET arrays difficult.
Novel OSCs were developed including 1,3,6,8-tetrakis(methylthio)pyrene (MT-pyrene). SCs of MT-pyrene grown by MAS and physical vapor transport (PVT) demonstrated very high mobility of >30 cm2 V-1 s-1 as OFETs. these results were selected as a cover picture for Advanced Materials.
Although MT-pyrene did not form droplets during MAS (not applicable for patterned growth), a novel method to potentially fabricate OFET arrays using SCs was found. In the new method based on MAS, the direct passes between source and target substrates are intentionally blocked, which highly improves uniformity of crystal growth. The application of this method to produce functioning "multi-SC" films was made into a new KAKENHI project (22K14293).
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