Exciplex-forming cohost systems with highly twisted hexaphenylbenzene-core donors for high-efficiency orange and red OLEDs

Chen, Yisheng; Wei, Wei‐Chih; Chen, Hao; Tsai, Tsung‐Lin; Hung, Wen‐Yi; Wong, Ken‐Tsung; Kung, Yu-Cheng

doi:10.1039/d2me00134a

Cited by 1 publication

(3 citation statements)

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“…According to the previous TADF kinetic studies 10 , 14 , assuming the pre-equilibrium between S 1 and T 1 states, the time-resolved fluorescence intensity, [S 1 ] f , can be expressed using the following equation: where I 0 is a proportional constant merging both radiative decay rate constant of the exciplex emission and instrument factor, τ 1 and τ 2 are the lifetime of the fast and slow decay component, respectively. Following this equation, the equilibrium constant K eq = K isc /K risc can be obtained by the ratio of the pre-exponential factor.…”

Section: Resultsmentioning

confidence: 99%

“…In this regard, the introduction of cyano group onto the acceptor is a preferred strategy because of the electron-withdrawing ability and short conjugation of cyano group can lower the LUMO and avoid the overly extend π-conjugation for a low triplet state, respectively. For instance, the triazene-based acceptor, CN-T2T, with m -benzonitrile to end-cap the triazine core possesses a high triplet state (2.82 eV), serving as a useful A for many exciplex systems 10 , 13 , 14 , 17 . Along this line, Cao et al .…”

Section: Introductionmentioning

confidence: 99%

“…1 ), are reported to serve as the acceptors for exciplex-forming blends. The rigid spiro-configured 27-DCN and 27-tDCN with two bulky tert -butyl phenyl groups are subject to blend with hexaphenylbenzene (HPB)-based bulky donors 14 , 28 – 30 . The exciplex of DDT-HPB: 27-tDCN and TATT: 27-tDCN blends gave the higher PLQY of 33% and 30% comparing to 19% and 18% for the DDT-HPB:27-DCN and TATT:27-DCN, implying the large steric effect of 27-tDCN is beneficial for a superior exciplex-forming system.…”

Section: Introductionmentioning

confidence: 99%

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

Chen,

Lin,

Huang

et al. 2024

Sci Rep

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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) λmax 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 λmax of 660 nm and maximum external quantum efficiency (EQEmax) of 5.8%, while EL λmax 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.

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Section: Resultsmentioning

confidence: 99%