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

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,C-2')iridium(acetylacetonate) [Ir(ppy)(2)acac] and iridium(III) bis(4-phenylthieno[3,2-c]pyridinato-N,C-2')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.