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Charge injection engineering of ambipolar field-effect transistors for high-performance organic complementary
Kang-Jun Baeg1, Juhwan Kim, Dongyoon Khim
1Department of Chemical Engineering, Hanbat National University, San 16-1, Dukmyung-dong, Yuseong-gu, Daejeon 305-719, Republic of Korea. kangjun100@etri.re.kr
ACS Applied Materials & Interfaces
|August 3, 2011
Summary
Researchers developed a new method using caesium salts to improve ambipolar organic field-effect transistors (OFETs). This technique enhances charge injection and transport, leading to high-performance complementary integrated circuits (CICs) with reduced power consumption.
Area of Science:
- Organic electronics
- Materials science
Background:
- Ambipolar polymers offer potential for low-cost, large-area manufacturing of complementary integrated circuits (CICs).
- Current ambipolar CICs face challenges including high static power consumption, low operating frequencies, and poor noise margins compared to unipolar transistor-based circuits.
Purpose of the Study:
- To demonstrate a method for controlling charge injection and transport in ambipolar organic field-effect transistors (OFETs) through electrical contact engineering.
- To improve the performance of ambipolar OFETs for practical CIC applications.
Main Methods:
- Engineered electrical contacts using solution-processed caesium (Cs) salts as electron-injection and hole-blocking layers.
- Modified the work function of gold (Au) electrodes from ~4.7 eV to ~4.1 eV using Cs salt interface modification.
- Fabricated and characterized ambipolar OFETs with controlled surface chemistry.
Main Results:
- Achieved excellent p-channel (hole mobility ~0.1-0.6 cm²/Vs) and n-channel (electron mobility ~0.1-0.3 cm²/Vs) characteristics using the same ambipolar polymer.
- Demonstrated highly suppressed counterpart charge carrier currents in depletion mode operation (I(off) < 70 nA at I(on) > 0.1-0.2 mA).
- Fabricated high-performance complementary inverters with high gain (>50) and high noise margin (>75% of ideal value), and ring oscillators with oscillation frequencies up to ~12 kHz.
Conclusions:
- Contact engineering with caesium salts significantly enhances charge injection and transport in ambipolar OFETs.
- The developed method enables high-performance, low-power complementary integrated circuits based on solution-processed ambipolar polymers.
- This approach overcomes key limitations of current ambipolar CICs, paving the way for advanced organic electronics.
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