Using Molecular Structure to Tune Intrachain and Interchain Charge Transport in Indacenodithiophene-Based Copolymers

Area of Science:

• Materials Science
• Organic Electronics
• Polymer Chemistry

Background:

• Rigid-rod polymers are crucial for organic electronics.
• Understanding charge transport mechanisms is key to developing efficient devices.
• Intrachain delocalization significantly impacts charge carrier mobility.

Purpose of the Study:

• To compare charge transport in two structurally similar polymers, p(IDT-BT) and p(IDT-BPD).
• To investigate the effect of intrachain delocalization on electronic transport properties.
• To elucidate the relationship between polymer structure and charge carrier mobility.

Main Methods:

• Quantum chemical calculations to assess torsional barriers and conjugation.
• Absorption and photoluminescence spectroscopy to determine energetic disorder.
• Charge modulation spectroscopy (CMS) and model calculations for charge carrier delocalization analysis.

Main Results:

• p(IDT-BPD) exhibits lower conjugation length and higher energetic disorder than p(IDT-BT).
• Charge carriers in p(IDT-BT) are substantially delocalized, occupying uniform energetic environments.
• p(IDT-BPD) shows poor interchain coupling, leading to charge carrier collapse and through-space tunneling.

Conclusions:

• High charge carrier mobility in p(IDT-BT) is attributed to significant 1D intrachain delocalization.
• Achieving high mobility on device-relevant scales is possible with controlled 1D delocalization.
• Structural differences profoundly influence charge transport mechanisms in organic semiconductors.