Exploiting Singlet Fission in Organic Light-Emitting Diodes

Ryo Nagata; Hajime Nakanotani; William J Potscavage Jr; Chihaya Adachi

doi:10.1002/adma.201801484

Exploiting Singlet Fission in Organic Light-Emitting Diodes

Adv Mater. 2018 Jul 5:e1801484. doi: 10.1002/adma.201801484. Online ahead of print.

Authors

Ryo Nagata^{1

2

3}, Hajime Nakanotani^{1

2

3

4}, William J Potscavage Jr^{1

2}, Chihaya Adachi^{1

2

3

4}

Affiliations

¹ Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka, 819-0395, Japan.
² JST, ERATO, Adachi Molecular Exciton Engineering Project, c/o Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka, 819-0395, Japan.
³ Department of Applied Chemistry, Kyushu University, 744 Motooka, Nishi, Fukuoka, 819-0395, Japan.
⁴ International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Nishi, Fukuoka, 819-0395, Japan.

PMID: 29974520
DOI: 10.1002/adma.201801484

Abstract

Harvesting of both triplets and singlets yields electroluminescence quantum efficiencies of nearly 100% in organic light-emitting diodes (OLEDs), but the production efficiency of excitons that can undergo radiative decay is theoretically limited to 100% of the electron-hole pairs. Here, breaking of this limit by exploiting singlet fission in an OLED is reported. Based on the dependence of electroluminescence intensity on an applied magnetic field, it is confirmed that triplets produced by singlet fission in a rubrene host matrix are emitted as near-infrared (NIR) electroluminescence by erbium(III) tris(8-hydroxyquinoline) (ErQ₃ ) after excitonic energy transfer from the "dark" triplet state of rubrene to an "emissive" state of ErQ₃ , leading to NIR electroluminescence with an overall exciton production efficiency of 100.8%. This demonstration clearly indicates that the harvesting of triplets produced by singlet fission as electroluminescence is possible even under electrical excitation, leading to an enhancement of the quantum efficiency of the OLEDs. Electroluminescence employing singlet fission provides a route toward developing high-intensity NIR light sources, which are of particular interest for sensing, optical communications, and medical applications.

Keywords: near-infrared phosphors; organic light-emitting diodes; singlet fission; triplet harvesting.