Dual mode transistors, the type of transistors that work in both depletion mode and enhancement mode, were reported more than 50 years ago using inorganic  semiconductors,  such  as  Silicon,  but  have  not  been  shown  in organic electronics. We report the first dual mode organic transistors based on organic electrochemical transistors (OECTs) using CPE-K, a self-doped conjugated polyelectrolyte, as the active material. The work stems from a key finding that CPE-K can be both doped and dedoped upon the interaction with anions and cations in an electrolyte, such as sodium chloride [i.e., table salt] dissolved in water. This property enables dual-mode functionality in OECTs, whose mode switching is accomplished by simply altering the polarity of the applied  gate  and  drain  voltages.  A  physical  model  for  the  device  was developed  to  explain  its  working  mechanism  and  correctly  predicts  its behavior in both operation modes. We also demonstrated the utilization of dual-mode  organic  transistors  in  reconfigurable  electronics  by  fabricating logic gates that could be switched between AND and NOR, and OR and NAND on the fly.

Impact:  Being  simple,  power  efficient,  and  compatible  with  high throughput microfabrication techniques, dual mode OECTs are a promising candidate  for  the  next  generations  of  efficient  computing  systems  and adaptive electronics.