2‐1: Invited Paper: Exciplex Host Engineering for High Efficiency and Stable Green PSF Technology

In this work, we designed and synthesized two new n‐type host materials, namely DPSiTrz and DTTrzDFph‐3, to establish an efficient and stable exciplex host system for green phosphorescence‐sensitized fluorescent (PSF) OLEDs. The optimized green PSF OLED utilizing BPP‐BCz: DPSiTrz and BPP‐BCz: DTTrzDFph‐3 as exciplex hosts reached impressive maximum EQE of 39.4% and 36.2%, respectively. The increased EQE of BPP‐BCz: DPSiTrz can be attributed to the high triplet (T1) energy of the exciplex host, which effectively prevents back energy transfer (BET) from the PS to the exciplex host. Furthermore, these devices demonstrated prolonged operational lifetimes (LT95) of 134 h and 380 h at 5000 cd/m 2 , respectively. Unlike EQE, the prolonged lifetime of the BPP‐BCz: DTTrzDFph‐3 is attributed to the intrinsic stability of the n‐type host material, which reduces device degradation.