New Exciplex‐forming Cohost Systems Harnessing Acceptors With Phenanthrene and Phenanthroline Core for Near‐Infrared OLEDs

Abstract Two new acceptors, C‐BPhCN and N‐BPhCN , with 2,3‐dicyanopyrazinophenanthrene and pyrazino[2,3‐f][1,10]phenanthroline‐2,3‐dicarbonitrile core and ortho‐linked biphenyl peripherals were synthesized and characterized. The exciplex formation of C‐BPhCN and N‐BPhCN as acceptor (A) and SBFC‐G1 as donor (D) was examined. Through optimization, the device using a D:A (2:1) blend in emitting layer (EML) exhibited maximum external quantum efficiency (EQE max ) of 8.26% and 5.25% with electroluminescence peak (EL λ max ) centered at 581 and 595 nm, respectively. A new D–A–D configured near‐infrared (NIR) fluorescent emitter DMACBBT was introduced as a dopant in the exciplex‐forming cohost system. By tuning the thickness of the electron transporting layer (ETL), the EQE max of the device employing SBFC‐G1: C‐BPhCN (2:1): 9 wt % DMACBBT as the EML reached 1.03% with EL λ max at 808 nm. The counterpart device utilizing SBFC‐G1: N‐BPhCN (2:1): 9 wt % DMACBBT as the EML exhibited an EQE max of 1.01% and EL λ max at 817 nm. The stability of the NIR OLED device was measured, yielding lifetimes ( T 60 ) of 182 and 126 h for SBFC‐G1: C‐BPhCN and SBFC‐G1 :N‐BPhCN cohost‐based devices, respectively. This work highlights the high efficiency of NIR OLEDs that can be practically realized by using the exciplex cohost systems with a tailor‐made NIR fluorescent emitter.