Designing molecules to bypass the singlet-triplet bottleneck in the electroluminescence of organic light-emitting-diode materials

TL;DR

This paper explores molecular design strategies to overcome the triplet bottleneck in OLEDs by incorporating elements with strong spin-orbit coupling, aiming to improve electroluminescence efficiency.

Contribution

It introduces new molecular structures derived from AlQ3 with enhanced spin-orbit coupling to bypass the triplet bottleneck in OLEDs.

Findings

Substituting N with As in AlQ3 derivatives yields favorable energy properties.

Boron substitution does not provide advantages over nitrogen.

Initial calculations support the potential of arsenic substitution for improved OLED performance.

Abstract

Electroluminescence in organic light emitting diode (OLED) materials occurs via the recombination of excitonic electrons-hole pairs Only the singlet excitons of commonly used OLED materials, e.g., Aluminum trihydroxyquinoline (AlQ$_3$), decay radiatively, limiting the external quantum efficiency to a maximum 25%. Thus 75% of the energy is lost due to the triplet bottleneck for radiative recombination. We consider molecules derived from AlQ$_3$ which bypass the triplet bottleneck by designing structures which contain strong spin-orbit coupling. As a first stage of this work, groundstate energies and vertical excitation energies of Al-arsenoquinolines and Al-boroarsenoquinolines are calculated. It is found that the substitution of N by As leads to very favourable results, while the boron substitution leads to no advantage.