Development of a deep-blue exciplex as an emitter and a host for highly efficient and wide-color OLEDs

Exciplex emission with thermally activated delayed fluorescence (TADF) characteristics has been widely applied in organic light-emitting diodes (OLEDs). Owing to its intermolecular charge transfer feature, development of an exciplex with a wide bandgap for deep-blue OLEDs is still challenging. Herein we designed a deep-blue exciplex system consisting of 3,3 '-di(9H-carbazol-9-yl) biphenyl (mCBP) and difluoroboron(Z)-3-(diphenylamino)-3-hydroxy-N,N-diphenylacrylamide (DNPhB) as the electron acceptor and the donor, respectively, which exhibit a deep-blue emission at 444 nm and a high photoluminescence quantum yield (PLQY) of 56%. The high triplet energy level enables the mCBP:DNPhB exciplex not only as a TADF emitter but also as a host with efficient Dexter energy transfer to a variety of phosphorescent molecules. A deep-blue OLED fabricated using the exciplex emitter shows the Commission Internationale de L'Eclairage (CIE) coordinates of (0.152, 0.075) as well as a high EQE of 4.83% and a high brightness up to 5486 cd m(-2). Moreover, wide-color phosphorescent OLEDs (PhOLEDs) were fabricated by using the exciplex as a host. The brightness of a green PhOLED based on the Ir(ppy)(3) emitter is up to 150 000 cd m(-2). This work paves the way to achieve a high-performance deep-blue exciplex OLED to meet the demand for potential applications such as a wide color display.

Automated summary

Researchers designed a deep-blue exciplex system consisting of mCBP and DNPhB, which not only exhibits thermally activated delayed fluorescence (TADF) characteristics but also acts as a host with efficient Dexter energy transfer. The OLED fabricated using this exciplex emitter shows excellent performance in brightness and color coordinates, making it suitable for potential applications such as wide color display.