Thiol Carbazole Self-Assembled Monolayers as Tunable Carrier Injecting Interlayers for Organic Transistors and...

Area of Science:

• Materials Science
• Organic Electronics
• Surface Chemistry

Background:

• Contact resistance at the metal-semiconductor interface is a major limitation for organic thin-film transistors (OTFTs).
• This issue impedes the performance of organic electronic devices and circuits.

Purpose of the Study:

• To address contact resistance in OTFTs by developing novel self-assembled monolayer (SAM) molecules.
• To engineer carrier-selective interlayers for improved charge injection in OTFTs.

Main Methods:

• Synthesis of three new thiol carbazole-based SAM molecules: tBu-2SCz, 2SCz, and Br-2SCz.
• Utilizing SAMs as interlayers to modify the work function of gold electrodes.
• Characterization using scanning tunneling microscopy (STM).
• Fabrication and testing of hole- and electron-transporting OTFTs and complementary inverters.

Main Results:

• SAMs successfully altered gold electrode work functions by over 1 eV.
• Br-2SCz formed ordered rows, achieving a high work function (5.48 eV), suitable for hole injection.
• tBu-2SCz formed a disordered layer with a low work function (4.52 eV), suitable for electron injection.
• Demonstrated improved operating characteristics in both p- and n-channel OTFTs.
• Successfully fabricated all-organic complementary inverters.

Conclusions:

• Thiol carbazole SAMs are versatile interlayers for enhancing carrier injection in OTFTs.
• This work presents a simple yet effective strategy for contact work function engineering.
• The developed SAMs show significant potential for advancing organic electronic devices and integrated circuits.