Threshold Voltage Control in Organic Field-Effect Transistors by Surface Doping with a Fluorinated Alkylsilane

Area of Science:

• Materials Science
• Organic Electronics
• Semiconductor Physics

Background:

• Organic field-effect transistors (OFETs) performance is tunable via doping to control charge carrier density.
• Surface doping offers a method to modify OFET characteristics post-fabrication.
• Conventional p-type dopants can be expensive and challenging to process.

Purpose of the Study:

• To investigate the efficacy of (tridecafluoro-1,1,2,2-tetrahydrooctyl)trichlorosilane (FTCS) as a surface dopant for OFETs.
• To compare the performance of FTCS doping via vapor deposition versus solution processing.
• To evaluate the control over doping magnitude and its impact on transistor parameters.

Main Methods:

• Fabrication of polycrystalline OFETs.
• Surface deposition of FTCS via vapor phase and solution processing.
• Electrical characterization of doped OFETs, including conductivity, threshold voltage, mobility, and I_ON/I_OFF ratio.

Main Results:

• Both vapor and solution deposition of FTCS resulted in p-type doping, evidenced by increased conductivity and positive threshold voltage shifts.
• The extent of doping could be precisely controlled by adjusting FTCS deposition time (vapor) or concentration (solution).
• Low doping levels maintained near-constant off-current and only slightly reduced mobility, with solution processing showing higher material and time efficiency.

Conclusions:

• FTCS is a cost-effective and processable alternative for p-type doping of OFETs.
• Surface doping with FTCS provides a controllable method to tune OFET performance.
• Solution-based FTCS doping presents a viable and industrially relevant approach for large-scale OFET manufacturing.