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Article: Strongly Luminescent Tetradentate Palladium(II)‐TADF Emitters. Blue TADF And TADF‐Sensitized OLEDs with External Quantum Efficiencies Over 23%
Title | Strongly Luminescent Tetradentate Palladium(II)‐TADF Emitters. Blue TADF And TADF‐Sensitized OLEDs with External Quantum Efficiencies Over 23% |
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Authors | |
Keywords | blue electroluminescence organic light emitting diodes palladium(II) thermally activated delayed fluorescence |
Issue Date | 15-Apr-2024 |
Publisher | Wiley |
Citation | Advanced Optical Materials, 2023, v. 12, n. 11 How to Cite? |
Abstract | Due to the low-lying Pd(4d)-orbitals, luminescent palladium(II) complexes usually show 3IL phosphorescence (IL = intraligand) with excited state lifetimes in the range of hundreds of microseconds, which limits their application in blue organic light-emitting diodes (OLEDs). Here, a molecular design strategy for the development of strongly luminescent Pd(II)-based thermally activated delayed fluorescence (TADF) emitters with fast radiative decay rate constants and reverse intersystem crossing rate (kRISC) constants is presented. The synthesized tetradentate [Pd(N*C*C^N)] TADF emitters show sky-blue to yellow (λmax = 484–565 nm) emission with excited state lifetimes in the range of 0.9−8.7 µs and high photoluminescence quantum yield of up to 77% in CH2Cl2 solution. In 5 wt.% 2,8-bis(diphenylphosphoryl)dibenzo[b,d]furan (PPF) thin films, these [Pd(N*C*C^N)] TADF complexes display blue to sky-blue (476−496 nm) emission with quantum yields close to unity. Variable-temperature emission lifetime measurements, femtosecond time-resolved spectroscopy, and density functional theory (DFT) and time-dependent DFT (TDDFT) calculations together reveal ultrafast kRISC rate constants of these [Pd(N*C*C^N)] TADF emitters. Using these Pd(II)-TADF emitters as dopants, sky-blue TADF and blue TADF-sensitized OLEDs with small efficiency roll-offs achieved high maximum external quantum efficiencies (EQEs) of 24.8% and 23.1%, respectively. |
Persistent Identifier | http://hdl.handle.net/10722/343525 |
ISSN | 2023 Impact Factor: 8.0 2023 SCImago Journal Rankings: 2.216 |
DC Field | Value | Language |
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dc.contributor.author | Sit, Man‐Ki | - |
dc.contributor.author | Tong, Glenna So Ming | - |
dc.contributor.author | Lam, Tsz‐Lung | - |
dc.contributor.author | Cheng, Gang | - |
dc.contributor.author | Hung, Faan‐Fung | - |
dc.contributor.author | So, Kwok‐Ming | - |
dc.contributor.author | Du, Lili | - |
dc.contributor.author | Choy, Kin‐On | - |
dc.contributor.author | Low, Kam‐Hung | - |
dc.contributor.author | Che, Chi‐Ming | - |
dc.date.accessioned | 2024-05-14T05:21:12Z | - |
dc.date.available | 2024-05-14T05:21:12Z | - |
dc.date.issued | 2024-04-15 | - |
dc.identifier.citation | Advanced Optical Materials, 2023, v. 12, n. 11 | - |
dc.identifier.issn | 2195-1071 | - |
dc.identifier.uri | http://hdl.handle.net/10722/343525 | - |
dc.description.abstract | <p>Due to the low-lying Pd(4d)-orbitals, luminescent palladium(II) complexes usually show <sup>3</sup>IL phosphorescence (IL = intraligand) with excited state lifetimes in the range of hundreds of microseconds, which limits their application in blue organic light-emitting diodes (OLEDs). Here, a molecular design strategy for the development of strongly luminescent Pd(II)-based thermally activated delayed fluorescence (TADF) emitters with fast radiative decay rate constants and reverse intersystem crossing rate (<em>k<sub>RISC</sub></em>) constants is presented. The synthesized tetradentate [Pd(N*C*C^N)] TADF emitters show sky-blue to yellow (λ<sub>max</sub> = 484–565 nm) emission with excited state lifetimes in the range of 0.9−8.7 µs and high photoluminescence quantum yield of up to 77% in CH<sub>2</sub>Cl<sub>2</sub> solution. In 5 wt.% 2,8-bis(diphenylphosphoryl)dibenzo[b,d]furan (PPF) thin films, these [Pd(N*C*C^N)] TADF complexes display blue to sky-blue (476−496 nm) emission with quantum yields close to unity. Variable-temperature emission lifetime measurements, femtosecond time-resolved spectroscopy, and density functional theory (DFT) and time-dependent DFT (TDDFT) calculations together reveal ultrafast <em>k<sub>RISC</sub></em> rate constants of these [Pd(N*C*C^N)] TADF emitters. Using these Pd(II)-TADF emitters as dopants, sky-blue TADF and blue TADF-sensitized OLEDs with small efficiency roll-offs achieved high maximum external quantum efficiencies (EQEs) of 24.8% and 23.1%, respectively.<br></p> | - |
dc.language | eng | - |
dc.publisher | Wiley | - |
dc.relation.ispartof | Advanced Optical Materials | - |
dc.rights | This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. | - |
dc.subject | blue electroluminescence | - |
dc.subject | organic light emitting diodes | - |
dc.subject | palladium(II) | - |
dc.subject | thermally activated delayed fluorescence | - |
dc.title | Strongly Luminescent Tetradentate Palladium(II)‐TADF Emitters. Blue TADF And TADF‐Sensitized OLEDs with External Quantum Efficiencies Over 23% | - |
dc.type | Article | - |
dc.identifier.doi | 10.1002/adom.202302308 | - |
dc.identifier.scopus | eid_2-s2.0-85179333728 | - |
dc.identifier.volume | 12 | - |
dc.identifier.issue | 11 | - |
dc.identifier.eissn | 2195-1071 | - |
dc.identifier.issnl | 2195-1071 | - |