Improving the efficiency of organic light emitting diodes by use of a diluted light-emitting layer

TL;DR

This paper demonstrates that incorporating a thin inert diluent mixed layer in organic light-emitting diodes significantly enhances external quantum efficiency, especially at low current densities, with up to 40% improvement.

Contribution

It introduces a novel approach of using a diluted light-emitting layer to improve OLED efficiency, analyzing effects of layer thickness and current density.

Findings

Maximum 40% efficiency increase with optimized layer thickness.

Efficiency enhancement is prominent at low current densities.

Luminescence quenching affects high current density performance.

Abstract

The use of a thin mixed layer consisting of an inert diluent material and a light emitting material between the hole-transport layer and electron-transport layer of organic light-emitting diodes leads to an increase in the external quantum efficiency. The efficiency improvement is highly dependent on the thickness of the diluted light-emitting layer and driving current. Significant improvement seen at low current densities is explained in terms of effective hole confinement by the mixed layer while a modest decreases in efficiency at higher current densities may be attributed to luminescence quenching at the hole-transport layer/inert diluents material interface. The phenomena are demonstrated with three different inert diluents materials. A maximum external quantum efficiency improvement of about 40% is found for a diluted light-emitting layer thickness between 40 {\AA} and 60 {\AA}.