Chen, Yi‐YunYi‐YunChenKung, Yu‐ChengYu‐ChengKungTsai, Cheng‐HanCheng‐HanTsaiWang, Chun‐KaiChun‐KaiWangLuo, DianDianLuoChen, Yi‐ShengYi‐ShengChenLiu, Shun‐WeiShun‐WeiLiuHsu, Allen Chu‐HsiangAllen Chu‐HsiangHsuHung, Wen‐YiWen‐YiHungWong, Ken‐TsungKen‐TsungWong2025-08-202025-08-202025-07-16https://scholars.lib.ntu.edu.tw/handle/123456789/731536This study explores new ternary exciplex-forming systems comprising a deep red-emitting CPF:58p-QN blend and various ratios of spacer TPF to optimize donor-acceptor interactions and exciplex characteristics. Time-resolved photoluminescence reveals delayed fluorescence of CPF:58p-QN:TPF blends, confirming the thermally activated delayed fluorescence (TADF) characters. By introducing different ratios of TPF, a progressive blueshift emission wavelength ranging from 696 nm (without TPF) to 659 nm (50 wt.% TPF) is observed. Notably, device A2, featuring CPF:58p-QN:TPF (2:2:1) blend as emitting layer, achieves a maximum external quantum efficiency (EQEmax) of 2.13% with the electroluminescent peak (EL λmax) centered at 672 nm. Moreover, a fluorescence emitter iCzPBBT is introduced as a dopant to realize a near-infrared (NIR) emissive device. Device B2, utilizing the CPF:58p-QN:TPF (2:2:1) blend as host doped with 5 wt.% iCzPBBT, exhibits an EQEmax of 1.35% (EL λmax = 848 nm), demonstrating effective energy transfer from exciplex to NIR dopant. Device C2 with a reduced amount of iCzPBBT (2 wt.%) to mitigate concentration quenching achieves an EQEmax of 1.72% (EL λmax = 834 nm) and good stability (LT90 > 88 h under a constant current density of 0.6 mA cm⁻2). This study underscores the potential of a ternary exciplex-forming system as a promising host for NIR OLED applications.enexciplexFÃrster resonance energy transfernear-infraredspacerthermally activated delayed fluorescence[SDGs]SDG7journal article10.1002/adom.202501258