Field-Dependent Charge Transport In Organic Thin-Film Transistors: Impact Of Device Structure And Organic Semiconductor Microstructure

Organic semiconductors are highly susceptible to defect formation, leading to electronic states in the gap-traps-which typically reduce the performance and stability of devices. To study these effects, we tuned the degree of charge trapping in organic thin-film transistors by modifying the film deposition procedures and device structure. The resulting charge carrier mobility varied between 10(-3) and 10cm(2)/Vs in 2,8-difluoro-5,11-bis(triethylsilylethynyl)anthradithiophene. We analyzed the data using a Poole-Frenkel-like model and found a strong dependence of mobility on the field in low-mobility transistors and a field-independent mobility in high-performance devices. We confirmed the presence of traps in all films investigated in this study and concluded that the Poole-Frenkel model is not sufficiently sensitive to identify traps when their concentration is below the detection limit.