Over 800 nm Emission via Harvesting of Triplet Excitons in Exciplex Organic Light-Emitting Diodes

Abstract

Triplet excitons can be utilized upon introduction of phosphors into exciplexes, and such a scenario has been studied in the development of high-performance near-infrared (NIR) organic light-emitting diodes (OLEDs). To generate exciplexes in an emitting layer (EML) in the device, commercially available phosphors bis­(2-phenylpyridinato-N,C2′)­iridium­(acetylacetonate) [Ir­(ppy)2acac] and iridium­(III) bis­(4-phenylthieno­[3,2-c]­pyridinato-N,C2′)­acetylacetonate (PO-01) were selected as donor components; in addition, a new designed fluorescent molecule, 3-([1,1′:3′,1″-terphenyl]-5′-yl)­acenaphtho­[1,2-b]­quinoxaline-9,10-dicarbonitrile (AQDC-tPh), and recently reported 3-([1,1′:3′,1″-terphenyl]-5′-yl)­acenaphtho­[1,2-b]­pyrazine-8,9-dicarbonitrile (APDC-tPh) were selected as acceptor components. An OLED with PO-01:AQDC-tPh blends as the EML has realized NIR emission at 750 nm and a maximum external quantum efficiency (EQE) of >0.23%. Furthermore, an OLED containing a PO-01:APDC-tPh blend realizes a maximum EQE of 0.16% at 824 nm. The high performance of these devices underlying phosphor-based exciplexes proves the potential and feasibility of our strategy for the construction of efficient NIR OLEDs.

Cationic Zinc(II) Complexes with Carbazole-Type Counter-Anions: Intracomplex Donor/Acceptor Pairs Affording Exciplexes with Thermally Activated Delayed Fluorescence

“…Metal complexes are potential donor or acceptor molecules, which have been used to assemble donor/acceptor pairs affording exciplexes. − It is noted that cationic metal complexes have rarely been used as acceptors for assembling donor/acceptor pairs . In cationic metal complexes, the complex cation and the counter-anion are closely bound together by strong electrostatic interactions between them.…”

High Performance Near-Infrared Emitters with Methylated Triphenylamine and Thiadiazolo[3,4-g]quinoxaline-Based Fluorophores

“…The tuning of the emission wavelength of organic light-emitting diodes (OLEDs) to the deep-red/near-infrared (DR/NIR) region has attracted widespread attention since DR/NIR light has a wide range of applications in night-vision displays, sensors and optical communications, as well as offering superior biocompatibility for medical systems [1][2][3][4][5]. To achieve this, tremendous efforts are devoted to achieving DR/NIR emission in the range of 650-900 nm from transition-metal complexes, boron dipyrromethene dyes and fluorescent materials with donor-acceptor (D-A) structures [5][6][7][8].…”

“…The results showed that the introduction of a single methyl group (2MeTPA-BT) made the HLCT properties more obvious. Herein, in order to obtain NIR electroluminescent materials, a [1,2,5]thiadiazolo [3,4g]quinoxaline acceptor, which had a stronger electron-withdrawing ability and larger conjugation, was selected to replace benzo[c] [1,2,5]thiadiazole. A D-A-D/D'-type emitter of 2MeTPA-QBT was synthesized by introducing a single methyl group into each D unit.…”

Heteroleptic Ir(III)-based near-infrared organic light-emitting diodes with high radiance capacity

“…Although new NIR emitters are continuously being designed for implementation of NIR OLEDs, the performance of NIR OLEDs is still far behind devices in the visible range due to energy gap law 9,10 . Many studies have been done to overcome the bottleneck of the intrinsic performance of NIR OLEDs, such as using thermally activated delayed fluorescence (TADF) [11][12][13][14][15] or using transition heavy metals such as Pt(II) [16][17][18][19][20] , Os(II) [21][22][23] , and Ir(III) [24][25][26][27][28][29][30] to obtain high efficiency. The method using TADF can transfer the non-radiative triplet exciton to the singlet space and obtain 100% of internal quantum efficiency (IQE).…”