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.