Charge-Transfer Complexes in Organic Field-Effect Transistors: Superior Suitability for Surface Doping

Area of Science:

• Materials Science
• Organic Electronics
• Surface Chemistry

Background:

• Organic field-effect transistors (OFETs) are crucial for flexible electronics.
• Improving charge carrier mobility and conductivity in OFETs is essential for device performance.
• Surface doping is a promising strategy to enhance OFET characteristics.

Purpose of the Study:

• To investigate the role of charge-transfer complexes in surface doping for OFETs.
• To compare the effectiveness of sequential deposition versus codeposition for doping OFETs.
• To understand the structural and electronic mechanisms behind improved OFET performance.

Main Methods:

• Fabrication of OFETs using 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) as the organic semiconductor.
• Doping of C8-BTBT using 2,2'-(perfluoronaphthalene-2,6-diylidene)dimalononitrile (F6TCNNQ) via sequential deposition and codeposition.
• Analysis of the resulting film morphology and crystalline structure.
• Characterization of the electronic properties and device performance of the OFETs.

Main Results:

• Sequential deposition of F6TCNNQ on C8-BTBT forms a cocrystalline structure at the surface, enhancing field-effect mobility and conductivity.
• This surface doping method significantly reduces the threshold voltage of the OFETs.
• Codeposition, even at low dopant concentrations (1 mol %), leads to decreased field-effect mobility, making it less suitable.
• The cocrystalline structure formed by sequential deposition maintains the integrity of the underlying thin-film structure.

Conclusions:

• Charge-transfer complexes are key to successful surface doping in OFETs.
• Sequential deposition is a superior method for doping OFETs compared to codeposition, leading to improved device performance.
• The formation of a cocrystalline structure is responsible for the enhanced electronic properties and device operation.