Field-effect carrier doping to organic molecular solids is discussed from view of organic transistor application and modification of physical properties. The organic field-effect transistors with high k gate dielectric and electric double layer capacitor (EDL) are investigated, and the low-voltage operation is realized at present stage. Furthermore, the trap states are fully discussed because carriers accumulated by electric-field first occupy the trap states. In this report, we show the future prospective for modification of physical properties of organic solids.
