Effects of Grain Boundary Density on the Gas Sensing Properties of Triethylsilylethynyl-Anthradithiophene Field-Effect Transistors

In this study, triethylsilylethynyl-anthradithiophene (TES-ADT) films with different density of grain boundaries are used for systematic investigation of effects of grain boundary density on gas sensing properties of TES-ADT field-effect transistors (FETs). Grain boundary density is simply controlled by changing mixing time of TES-ADT solution. Higher mixing time leads to higher grain boundary density, and field-effect mobility decreases with increased grain boundary density. However, gas sensing properties exhibit the opposite behavior. Drain current and field-effect mobility of FETs based on TES-ADT film with higher grain boundary density increase much more upon exposure of NO2 with electron withdrawing character. In addition, dynamic gas sensing tests reveal that response rate and sensitivity of a TES-ADT sensor are enhanced remarkably by an increase of grain boundary density in TES-ADT films. Grain boundaries provide a pathway for diffusion of gas molecules into channel regions and thus increase of grain boundary density is beneficial for development of highly sensitive OFET gas sensors.