Efficient charge injection in p-type polymer field-effect transistors with low-cost molybdenum electrodes through...

Area of Science:

• Materials Science
• Organic Electronics
• Semiconductor Physics

Background:

• Polymer organic field-effect transistors (OFETs) are crucial for low-cost electronics.
• Molybdenum (Mo) electrodes are cost-effective but suffer from poor charge injection in OFETs.
• High work function metals like gold (Au) provide better charge injection but are expensive.

Purpose of the Study:

• To investigate the use of a vanadium pentoxide (V2O5) thin film as an interlayer to improve charge injection in Mo-based polymer OFETs.
• To enhance the performance of polymer OFETs using low-cost Mo electrodes.
• To understand the mechanism of improved charge injection facilitated by the V2O5 interlayer.

Main Methods:

• Fabrication of polymer OFETs using regioregular poly(3-hexylthiophene) (rr-P3HT) and a p-type polymer semiconductor (PC12TV12T).
• Incorporation of a thermally deposited V2O5 thin film interlayer between the Mo electrode and the polymer semiconductor.
• Characterization of device performance, including charge carrier mobility.
• Analysis of electrode work function modification using ultraviolet photoelectron spectroscopy (UPS).

Main Results:

• Polymer OFETs with a bare Mo electrode showed significantly lower charge carrier mobility compared to Au electrodes due to a large hole injection barrier (0.5-1.0 eV).
• The incorporation of a V2O5 interlayer on Mo electrodes resulted in charge carrier mobility comparable to pristine Au electrodes.
• The best performing devices with a 5 nm V2O5 interlayer achieved mobilities of 0.12 cm²/Vs for P3HT and 0.38 cm²/Vs for PC12TV12T.
• UPS measurements indicated that the work function of Mo increased from 4.3 eV to 4.9 eV with increasing V2O5 thickness, reducing the injection barrier.

Conclusions:

• The V2O5 interlayer effectively lowers the hole injection barrier between Mo electrodes and p-type polymer semiconductors.
• This V2O5 interlayer enables high-performance polymer OFETs using low-cost Mo electrodes, making them comparable to those with expensive Au electrodes.
• The findings pave the way for developing large-area, cost-effective electronic devices utilizing Mo electrodes and V2O5 interlayers.