Polymer Electret Improves the Performance of the Oxygen-Doped Organic Field-Effect Transistors

Chemical doping is widely used in the electronic devices. In p-type semiconductor thin films, oxygen doping fills the hole traps and increases hole concentrations, improving the performance of the organic field-effect transistors (OFETs). Due to the low ionization potential for p-type semiconductors, the superfluous holes induced by the oxygen doping degrades the OFETs off-state leakage performance. On the other hand, for p-type semiconductors with a high ionization potential (up to 5.5-6.0 eV), the limited oxidation of oxygen is hard to achieve satisfactory doping concentrations to fill the trap states. This refers to the well-known intrinsic incompatibility between the oxygen doping and high-performance OFETs. Herein, a combined strategy using the oxygen doping and polymer electret is introduced to achieve the high-performance OFETs. That is, moderate hole concentrations induced by low-pressure (30 Pa) oxygen plasma fills the hole traps within semiconductor. While the built-in field induced by polymer electret accumulates the holes inside semiconductor near the semiconductor/electret interface, further improving the OFETs performance. Using a model semiconductor with high ionization potential-2,7-didodecyl[1]benzothieno[3,2-b][1]benzothiophene (C12-BTBT) as an example, the high-performance OFETs with field-effect mobility (μFET) of 3.5 cm2 V-1 s-1, subthreshold-swing (SS) of 110 mV decade-1, on-off ratio of 104, and widely-tunable threshold voltage (Vt) are realized at a low voltage below 2 V in the open air.