We present herein a linear expanded pi-conjugation system comprising azulene units: 2,6':2',6"-terazulene. This simple hydrocarbon exhibits excellent n-type transistor performance with an electron mobility of up to 0.29 cm(2) V-1 s(-1). The lowest unoccupied molecular orbital (LUMO) is well distributed over the entire molecule, whereas the highest occupied molecular orbital (HOMO) is localized at one end. These findings indicate a disadvantage of hole carrier transport and an advantage of n-type-specific transport behavior. This system presents an unconventional concept: polarity control of OFET by molecular orbital distribution control.