High‐Efficiency Near‐Infrared OLED Enabled by Exciplex‐Forming Hosts and a New Organic Fluorescent Emitter
Yiyun Chen, Yu‐Cheng Kung, Miaosheng Wang, Yuan‐Chih Lo, Yao‐Te Chia, Chun‐Kai Wang, Deng‐Gao Chen, Ju‐Ting Cheng, Pi‐Tai Chou, Chi-Chi Wu, Elise Y. Li, Bin Hu, Wen‐Yi Hung, Ken‐Tsung Wong
Abstract
Abstract Two blends comprising new dicyanopyrazine‐based acceptors ( m ‐CN and p ‐CN ) and a carbazole‐based donor CPTBF are explored for exciplex formation. The CPTBF: m ‐CN and CPTBF: p ‐CN blends show the signature red‐shifted emission together with the delayed fluorescence observed in time‐resolved measurement, manifesting the characteristics of thermally activated delayed fluorescence (TADF). The electroluminescence (EL) device employing CPTBF: m ‐CN ( CPTBF: p ‐CN ) blend as the emitting layer (EML) achieved an EQE of 5.22% (2.05%) with the EL λ max centered at 607 nm (625 nm). The exciplex excitons can be efficiently extracted by a new benzobisthiadiazole‐based near‐infrared (NIR) emitter DCzPBBT , where a device is configured with CPTBF: m ‐CN : (5 wt.%) DCzPBBT as the EML to achieve a high EQE of 5.32% and an EL λ max 758 nm. Further increase of the doping concentration to 10 wt.% of DCzPBBT exhibits a bathochromic shifted EL λ max to 772 nm with 94% spectral coverage in the NIR (>700 nm) region, while the device EQE retains at 4.06%. The superior device performance stems from the highly efficient energy transfer between the exciplex‐forming host and NIR dopant together.