Effect of Density of States on Mobility in Small-Molecule n-Type Organic Thin-Film Transistors Based on a Perylene Diimide

Bottom-contact organic thin-film transistors with active layers made of n-type small-molecule perylene diimide Polyera ActivinkTM N1400 were fabricated and were compared with those of 6,13-bis (triisopropylsilylethinyl)pentacene and poly(triarylamine) (PTAA). For the three devices, the mobility values and the distribution of the density of states (DOS) were estimated from current-voltage measurements. The mobility value of the N1400 samples increases up to four orders of magnitude within the measured voltage range, reaching the PTAA mobility values at high gate voltages. Finally, we analyze the effect of the distribution of the DOS on the mobility by studying the free-charge sheet concentration.