Organic Thin Film Transistors Based on 2,3-Dimethylpentacene and 2,3-Dimethyltetracene.

2,3-Dimethylpentacene (DMP) and 2,3-dimethyltetracene (DMT) were synthesized, characterized and employed as the channel material in the fabrication of thin-film transistors. The two methyl groups increase the chemical stability of the compounds versus the pristine acene analogues. The crystals maintain herringbone-like molecular packing, whereas the weak dipole associated with the unsymmetrical molecule induces an anti-parallel alignment among the neighbors. This structural motif favors layered film growth on SiO₂/Si surface. Thin film transistors prepared on SiO₂/Si and n-nonyltrichlorosilane-modified SiO₂/Si at different substrate temperatures were compared. DMP-based transistors prepared on rubbed n-nonyltrichlorosilane-modified SiO₂/Si substrate gave the highest field-effect mobility of 0.46 cm²/Vs, whereas DMT-based transistor gave a mobility of 0.028 cm²/Vs. [ABSTRACT FROM AUTHOR]