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Design rules for high mobility xanthene-based hole transport materials
Daniel P Tabor1, Valerie A Chiykowski2, Pascal Friederich1,3,4
1Department of Chemistry and Chemical Biology , Harvard University , 12 Oxford St. , Cambridge , MA 02138 , USA .
Chemical Science
|December 6, 2019
Summary
Researchers developed new spiro[fluorene-9,9'-xanthene]-based materials for organic electronics. Functional group size impacts hole mobility by controlling disorder, offering design rules for improved performance in devices like organic light-emitting diodes and perovskite solar cells.
Area of Science:
- Materials Science
- Organic Electronics
- Solid-State Physics
Background:
- Tunable, conductive hole transport materials (HTMs) are essential for high-performance organic electronics, including organic light-emitting diodes (OLEDs) and perovskite solar cells (PSCs).
- Commercial viability demands HTMs with facile synthesis, high charge carrier mobility, and precisely controlled electronic energy levels, particularly the highest occupied molecular orbital (HOMO).
Purpose of the Study:
- To systematically investigate a novel class of spiro[fluorene-9,9'-xanthene]-based organic semiconductors as potential HTMs.
- To establish structure-property relationships between side group functionalization and key material characteristics like HOMO energy and hole mobility.
- To derive general design principles for enhancing charge carrier mobility in organic electronic materials.
Main Methods:
- Synthesis of spiro[fluorene-9,9'-xanthene] derivatives with systematic side group modifications.
- Characterization of electronic properties, including HOMO energy levels.
- Measurement of charge carrier mobility.
- Computational analysis using bulk simulations to understand structure-disorder-mobility relationships.
Main Results:
- Demonstrated that side group functionalization effectively tunes HOMO energy and charge carrier mobility.
- Identified that larger, sterically hindering groups (e.g., methyl) reduce conformational disorder, thereby increasing hole mobility.
- Showed that highly asymmetric or polar groups (e.g., fluorine) increase electrostatic disorder, leading to reduced hole mobility.
Conclusions:
- The study provides generalizable design rules for optimizing organic HTMs based on spiro[fluorene-9,9'-xanthene] scaffolds.
- These findings facilitate the rational design of next-generation HTMs with enhanced performance for OLEDs and PSCs.
- The derived principles will guide future development of efficient and stable organic electronic devices.
