Exceptionally high charge mobility in phthalocyanine-based poly(benzimidazobenzophenanthroline)-ladder-type...

Area of Science:

• Materials Science
• Organic Electronics
• Polymer Chemistry

Background:

• Two-dimensional conjugated polymers (2DCPs) are promising for organic electronics but often have limited charge mobility due to poor π-conjugation.
• Existing 2DCPs, like π-conjugated covalent organic frameworks, struggle to achieve high charge carrier mobilities.

Purpose of the Study:

• To overcome the limitations of current 2DCPs by developing novel materials with enhanced charge transport properties.
• To synthesize and characterize new phthalocyanine-based ladder-type 2DCPs for improved performance in organic optoelectronics.

Main Methods:

• Synthesis of 2DCPs via polycondensation of octaaminophthalocyaninato metal(II) and naphthalenetetracarboxylic dianhydride under solvothermal conditions.
• Optical bandgap measurement and density functional theory (DFT) calculations to analyze electronic structure and effective masses.
• Terahertz spectroscopy to investigate charge carrier transport mechanisms and mobility.

Main Results:

• Demonstrated synthesis of two-dimensional semiconducting phthalocyanine-based poly(benzimidazobenzophenanthroline)-ladder-type 2DCPs (2DCP-MPcs).
• Observed optical bandgaps of ~1.3 eV with highly delocalized π-electrons and small electron-hole reduced effective masses (~0.15m₀).
• Achieved exceptionally high sum mobility of electrons and holes (~970 cm² V⁻¹ s⁻¹) via Drude-type free carrier transport.

Conclusions:

• Effective π-conjugation is crucial for enhancing charge transport in 2DCPs.
• The developed 2DCP-MPcs demonstrate superior charge transport properties compared to existing linear conjugated polymers and 2DCPs.
• These high-mobility 2DCPs hold significant potential for future organic optoelectronic applications.