Simulating charge transport in tris(8-hydroxyquinoline) aluminium (Alq(3))

Area of Science:

• Materials Science
• Organic Electronics
• Computational Chemistry

Background:

• Understanding charge transport in organic semiconductors is crucial for developing advanced electronic devices.
• Tris(8-hydroxyquinoline) aluminium (Alq(3)) is a widely used material in organic light-emitting diodes and other organic electronics.
• Accurate prediction of charge mobility requires consideration of molecular packing and electronic structure.

Purpose of the Study:

• To present a novel model for charge transport in organic solids.
• To simulate time-of-flight mobility measurements in crystalline and disordered Alq(3) films.
• To elucidate the factors governing electron and hole mobility differences.

Main Methods:

• Molecular-scale modeling of film morphology.
• Density functional theory (DFT) for calculating electronic couplings.
• Simulation of time-of-flight mobility measurements.

Main Results:

• Predicted electron mobilities of ~1 cm(2) V(-1) s(-1) for crystalline Alq(3) and ~10(-4) cm(2) V(-1) s(-1) for disordered Alq(3).
• Electron mobilities are approximately two orders of magnitude greater than hole mobilities.
• Identified dominant charge transport pathways in disordered Alq(3) films.

Conclusions:

• The developed model accurately predicts charge transport properties without fitting parameters.
• The spatial extent of frontier orbitals explains the significant difference between electron and hole mobilities.
• Charge transport in disordered Alq(3) is facilitated by a few highly conductive molecular pathways.