Exciplex-forming cohost systems with 2,7-dicyanofluorene acceptors for high efficiency red and deep-red OLEDs

Yi-Sheng Chen; I-Hung Lin; Hsin-Yuan Huang; Shun-Wei Liu; Wen-Yi Hung; Ken-Tsung Wong

doi:10.1038/s41598-024-52680-6

Exciplex-forming cohost systems with 2,7-dicyanofluorene acceptors for high efficiency red and deep-red OLEDs

Sci Rep. 2024 Jan 30;14(1):2458. doi: 10.1038/s41598-024-52680-6.

Authors

Yi-Sheng Chen^{1

2}, I-Hung Lin³, Hsin-Yuan Huang³, Shun-Wei Liu¹, Wen-Yi Hung⁴, Ken-Tsung Wong^{5

6}

Affiliations

¹ Organic Electronic Research Center, Ming Chi University of Technology, New Taipei City, 24031, Taiwan.
² Department of Chemistry, National Taiwan University, Taipei, 10617, Taiwan.
³ Department of Optoelectronics and Materials Technology, National Taiwan Ocean University, Keelung, 20224, Taiwan.
⁴ Department of Optoelectronics and Materials Technology, National Taiwan Ocean University, Keelung, 20224, Taiwan. wenhung@mail.ntou.edu.tw.
⁵ Department of Chemistry, National Taiwan University, Taipei, 10617, Taiwan. kenwong@ntu.edu.tw.
⁶ Institute of Atomic and Molecular Science Academia Sinica, Taipei, 10617, Taiwan. kenwong@ntu.edu.tw.

Abstract

Two 2,7-dicyaonfluorene-based molecules 27-DCN and 27-tDCN are utilized as acceptors (A) to combine with hexaphenylbenzene-centered donors (D) TATT and DDT-HPB for probing the exciplex formation. The photophysical characteristics reveal that the steric hindered 27-tDCN not only can increase the distance of D and A, resulting in a hypsochromic emission, but also dilute the concentration of triplet excitons to suppress non-radiative process. The 27-tDCN-based exciplex-forming blends exhibit better photoluminescence quantum yield (PLQY) as compared to those of 27-DCN-based pairs. In consequence, among these D:A blends, the device employing DDT-HPB:27-tDCN blend as the emissiom layer (EML) exhibits the best EQE of 3.0% with electroluminescence (EL) λ_max of 542 nm. To further utilize the exciton electrically generated in exciplex-forming system, two D-A-D-configurated fluorescence emitter DTPNT and DTPNBT are doped into the DDT-HPB:27-tDCN blend. The nice spectral overlap ensures fast and efficient Förster energy transfer (FRET) process between the exciplex-forming host and the fluorescent quests. The red device adopting DDT-HPB:27-tDCN:10 wt% DTPNT as the EML gives EL λ_max of 660 nm and maximum external quantum efficiency (EQE_max) of 5.8%, while EL λ_max of 685 nm and EQE of 5.0% for the EML of DDT-HPB:27-tDCN:10 wt% DTPNBT. This work manifests a potential strategy to achieve high efficiency red and deep red OLED devices by incorporating the highly fluorescent emitters to extract the excitons generated by the exciplex-forming blend with bulky acceptor for suppressing non-radiative process.