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Crystallisation-enhanced bulk hole mobility in phenothiazine-based organic semiconductors
D B Shinde1,2, Jagadish K Salunke3, Nuno R Candeias3
1Polymer Science and Engineering Division, CSIR-National Chemical Laboratory, Dr Homi Bhabha Road, Pune 411008, India.
Scientific Reports
|April 13, 2017
Summary
Novel phenothiazine derivatives were synthesized. While C(7) substitution hindered film ordering and charge mobility, the unsubstituted compound achieved record mobility, highlighting the importance of molecular packing for organic electronics.
Area of Science:
- Organic Chemistry
- Materials Science
- Physical Chemistry
Background:
- Phenothiazine derivatives are crucial in organic electronics.
- Developing new materials with high charge carrier mobility is essential for advancing organic electronic devices.
- Understanding structure-property relationships is key to designing efficient organic semiconductors.
Purpose of the Study:
- To synthesize novel donor-acceptor systems based on C(3)-malononitrile-substituted phenothiazines.
- To characterize their thermal, spectroscopic, and electrochemical properties.
- To investigate the impact of C(7) substitution on molecular ordering and charge transport.
Main Methods:
- Multi-step synthesis involving Ullmann-coupling, Vilsmeier-Haack formylation, Knoevenagel-condensation, and Suzuki-coupling.
- Spectroscopic (UV-Vis, NMR, etc.) and electrochemical (cyclic voltammetry) characterization.
- Thin-film preparation and charge mobility measurements.
- Computational conformational analysis.
Main Results:
- Three novel C(3)-malononitrile-substituted phenothiazine systems were successfully synthesized.
- C(7) aryl substitution resulted in amorphous films with typical phenothiazine hole mobilities.
- The C(7)-unsubstituted analogue formed highly ordered films with a record hole mobility of 1 × 10⁻³ cm² V⁻¹ s⁻¹.
- Computational studies indicated that C(7) substituent rotation disrupts molecular ordering.
Conclusions:
- Molecular packing significantly influences charge carrier mobility in phenothiazine-based materials.
- Free rotation of C(7) substituents hinders the formation of ordered films necessary for high mobility.
- The C(7)-unsubstituted 3-malononitrile phenothiazine represents a promising material for organic electronic applications due to its exceptional charge transport properties.
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