Gate voltage impact on charge mobility in end-on stacked conjugated oligomers

Area of Science:

• Organic electronics
• Condensed matter physics
• Materials science

Background:

• Organic field-effect transistors (OFETs) are crucial for flexible electronics.
• Understanding charge transport mechanisms in the active channel is key to device performance.
• Existing models often simplify the complex interplay of charge carriers within conjugated polymers.

Purpose of the Study:

• To develop a comprehensive model for charge transport in thin-film OFETs with end-on-oriented conjugated polymer chains.
• To investigate the influence of gate and source-drain voltages on charge mobility.
• To elucidate the fundamental processes governing charge carrier movement in the semiconductor channel.

Main Methods:

• Simulated charge transport within a 25-polymer chain model.
• Calculated delocalized quantum orbital eigenstates for on-chain hole distribution.
• Employed semi-classical methods for inter-chain charge transfer.
• Determined self-consistent charge density and electric field distributions.

Main Results:

• Observed a non-monotonic dependence of charge mobility on gate voltage, with initial increases followed by decreases.
• Identified the formation of a second resonant peak in mobility at higher gate voltages.
• Demonstrated that charge transport involves both inter-chain hole transfer and on-chain coherence transfer.

Conclusions:

• The presented model provides a more nuanced understanding of charge transport in OFETs.
• Charge mobility is influenced by complex interactions, including coherence transfer along polymer chains.
• The model offers insights applicable to novel vertical OFET architectures.