MA02.01.04 : A Multilayer Approach To Enhance Charge Injection In Organic Field Effect Transistors

11:45 AM–12:00 PM Apr 3, 2018 (America - Denver)

PCC West, 100 Level, Room 102 BC

Diego Nava1 2 Alberto Scaccabarozzi1 Mario Caironi1

1, Istituto Italiano di Tecnologia, Milan, , Italy
2, Politecnico di MIlano, Milan, , Italy

Organic field effect transistors, OFETs, have attracted extensive interest over the past years thanks to the promise of realize solution-process, flexible and low-cost electronics. Despite all the efforts in optimizing OFETs performances, achieve efficient charge injection from the electrodes is still an open challenge. Such contact performance is the most seriously concern for short-channel devices, with channel length typically less than few micrometres, though they are extremely attractive because of their high-frequency operation and the possibility of high-density integration. In a typical silicon based MOFET, heavily doped regions, close to the Source-Drain electrodes, promote the charge injection. Attempting to reproduce this architecture into organic devices, a wide number of possible methods have been proposed, laying on different doping techniques but mostly of them require high vacuum evaporation and masking systems.
In this work, we present a multilayer structure for the reduction of the injection barrier in Bottom-Contact Top-Gate Field Effect Transistor. A highly doped semiconductor layer - poly{[N,N0-bis(2-octyldodecyl)-naphthalene- 1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,50-(2,20-bithiophene)} (P(NDI2OD-T2)) blended with electrically insulating material, high-density polyethylene (HDPE) and doped with dihydro-1H-benzoimidazol-2-yl (N-DBI) derivative - act as injection layer while the FET depleted channel is created in an upper layer of pristine P(NDI2OD-T2) formed on top of the previous.
We show, how the addition of HDPE is crucial to overcome the doping diffusion inside the active channel region and in which way OFETs characteristics are enhanced, from contact resistance subthreshold swing. Finally, we will show how this approach can be extended also to p-type organic semiconductors, acting as a versatile method to reduce the injection barrier issue in OFETs.