Organic light-emitting diodes using open-shell molecule as emitter: the emission from doublet

TL;DR

This paper reports the development of OLEDs using a stable open-shell molecule, BDPA, as the emitter, which emits from a doublet state, bypassing traditional triplet harvesting issues and achieving high luminance comparable to existing OLED technologies.

Contribution

The study introduces the use of a stable open-shell molecule as an OLED emitter, demonstrating emission from a doublet state and achieving high luminance, a novel approach in OLED design.

Findings

Maximum luminance of 4879 cd/m2 achieved

Emission confirmed from LUMO to SOMO transition

Open-shell molecule enables spin-allowed radiative decay

Abstract

We fabricate OLEDs using a stable neutral {\pi} radical, BDPA, as the emitter. There is only one electron in the singly occupied molecular orbital (SOMO) of this open-shell molecule. This feature makes the excited state of open-shell molecules be neither singlet nor triplet, but doublet. The key issue of how to harvest the triplet energy in an OLED is thus bypassed, due to the radiative decay of doublet is totally spin allowed. In the BDPA-based OLED, the emission was confirmed to be from the electronic transition from LUMO to SOMO, via the frontier molecular orbital analysis combined with the spectroscopy measurements. The maximum luminance of the OLEDs is 4879 cd/m2 which is comparable to the first reported Fluorescence-, Phosphorecence- and TADF-based OLEDs.