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

• Published in: IEEE electron device letters 2020-11, Vol.41 (11), p.1665-1668
• Main Authors: Li, Dongfan, Zhu, Yuanwei, Wei, Peng, Lu, Wanlong, Li, Shengtao, Wang, Steven, Xu, Ben Bin, Lu, Guanghao
• Format: Article
• Language: English
• Subjects: Benzothiophene; Doping; Electrets; Electronic devices; Field effect transistors; Hole traps; Incompatibility; Ionization potentials; Logic gates; Low pressure; Low voltage; OFETs; Organic field-effect transistor; organic semiconductor; Oxidation; Oxygen plasma; P-type semiconductors; Performance enhancement; Plasmas; polymer electret; Polymers; Programmable logic arrays; Semiconductor devices; Semiconductors; Thin films; Threshold voltage; Transistors
• ISSN: 0741-3106; 1558-0563
• DOI: 10.1109/LED.2020.3026486

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 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 novel strategy is introduced to overcome the incompatibility and achieve high-performance OFETs by using the structural polymer electret. That is, moderate hole concentrations induced by low-pressure (30 Pa) oxygen plasma fill the hole traps within semiconductor. And the built-in field resulted from polymer electret accumulates the holes inside semiconductor near the semiconductor/electret interface, thus improving the OFETs performance. Using a model organic semiconductor with high ionization potential-2,7-didodecyl[1]benzothieno [3,2-b][1]benzothiophene (C 12 -BTBT) as an example, the high-performance OFETs with field-effect mobility ( \mu _{FET} ) of 3.5 cm 2 V −1 s −1 , subthreshold-swing ( SS ) of 110 mV decade −1 , on-off ratio of 10 4 , and widely-tunable threshold voltage ( {V} _{t} ) are realized at a low voltage below 2 V in the open air.