Engineering Asymmetric Charge Injection/Extraction to Optimize Organic Transistor Performances

Area of Science:

• Materials Science
• Organic Electronics
• Surface Chemistry

Background:

• Organic field-effect transistors (OFETs) are crucial for flexible electronics.
• Enhancing charge injection/extraction at the electrode/organic semiconductor interface is key to improving OFET performance.
• Self-assembled monolayers (SAMs) offer a versatile tool for interface engineering.

Purpose of the Study:

• To investigate the impact of asymmetric electrode functionalization on OFET electrical properties.
• To optimize charge injection and extraction using different SAMs on source/drain electrodes.
• To correlate interface modifications with device performance metrics like mobility and contact resistance.

Main Methods:

• Fabrication of five types of OFETs: pristine, symmetrically functionalized (TP-S/D, PFBT-S/D), and asymmetrically functionalized (PFBT-S/TP-D, TP-S/PFBT-D) electrodes.
• Utilizing thiophenol (TP) and pentafluorobenzenethiol (PFBT) SAMs for electrode functionalization.
• Characterization of device performance, including field-effect mobility (μFET) and contact resistance (RC).

Main Results:

• The asymmetric PFBT-S/TP-D configuration achieved a field-effect mobility of 0.86 ± 0.23 cm² V⁻¹ s⁻¹, approximately three times higher than the pristine case (0.31 ± 0.12 cm² V⁻¹ s⁻¹).
• The asymmetric PFBT-S/TP-D OFET exhibited a contact resistance that was 10-fold lower than the TP-S/PFBT-D case and over five times lower than the pristine case.
• Asymmetric functionalization significantly impacted additional hole density, surface potential, and effective work function, correlating with mobility enhancements.

Conclusions:

• Asymmetric functionalization of source/drain electrodes with specific SAMs is a highly effective strategy for enhancing OFET performance.
• The PFBT-S/TP-D interface modification offers a promising route to significantly improve charge transport and reduce contact resistance in OFETs.
• These findings provide valuable insights for advancing the performance of organic electronic devices, including transistors, solar cells, and sensors.