Direct measurement of the magnetic field effects on carrier mobilities and recombination in tri-(8-hydroxyquinoline)-aluminum based light-emitting diodes

TL;DR

This study investigates how magnetic fields influence carrier mobilities and recombination in Alq3-based LEDs, revealing that magnetic fields mainly affect singlet-triplet interconversion rather than mobilities.

Contribution

It provides direct measurements showing magnetic fields do not alter mobilities but reduce recombination, highlighting the interconversion mechanism as the primary effect.

Findings

Magnetic fields do not affect electron and hole mobilities.

Magnetic fields decrease the electron-hole recombination coefficient.

Interconversion between singlet and triplet pairs is the main mechanism.

Abstract

The magnetic field effects on the carrier mobilities and recombination in tri-(8-hydroxyquinoline)-aluminum (Alq3) based light-emitting diodes have been measured by the method of transient electroluminescence. It is confirmed that the magnetic field has no effect on the electron and hole mobilities in Alq3 layers and can decrease the electron-hole recombination coefficient. The results imply that the dominant mechanism for the magnetic field effects in Alq3 based light-emitting diodes is the interconversion between singlet e-h pairs and triplet e-h pairs modulated by the magnetic field when the driving voltage is larger than the onset voltage of the electroluminescence.