Intrinsically-ionic donor-acceptor molecules featuring thermally-activated delayed fluorescence for high-performance host-guest blue light-emitting electrochemical cells

Pang, Xianchun; Zhang, Ke; Song, Yu; Yue, Xiu; Yu, Renyou; He, Lei

doi:10.1016/j.cej.2022.137987

Cited by 11 publications

(7 citation statements)

References 64 publications

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“…All emitters were synthesized according to the previously obtained di-iridium chlorobridged dimer, [Ir(dfppz) 2 (m-Cl)] 2 , in the presence of different ancillary ligands under inert conditions 54,55 as illustrated in Schemes S1 and S2 (ESI †). Two complexes were structurally characterized by 1 H, 13 C NMR, 2D NMR and ESI-mass spectral studies (see Fig. S1-S9, ESI †).…”

Section: Synthesis and X-ray Crystal Structuresmentioning

confidence: 99%

“…3,6,7 Over the past two decades, significant efforts have been devoted to accelerating the development of LECs including the material molecular designs, device fabrication techniques, as well as operation mechanism studies. 2,[8][9][10][11][12][13][14] Harvesting both electrogenerated singlet exciton and triplet exciton, in principle, can achieve 100% internal quantum efficiency during the conversion process from electron to photon. [15][16][17] As a result, the efficiencies of LECs have been significantly improved, especially for those based on the ionic transition metal complexes (iTMCs) with the efficient spin-orbit coupling effect.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Dinuclearization strategy of cationic iridium(iii) complexes for efficient and stable flexible light-emitting electrochemical cells

et al. 2023

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Section: Synthesis and X-ray Crystal Structuresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Dinuclearization strategy of cationic iridium(iii) complexes for efficient and stable flexible light-emitting electrochemical cells

et al. 2023

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“…Recently, a novel type of fluorescent materials with thermally activated delayed fluorescence (TADF) [32] has been demonstrated to be capable of recycling the triplet excitons on them via efficient reverse intersystem crossing (RISC), leading to phosphorescent EL efficiencies. In view of such a high potential, neat-film [33][34][35][36] and host-guest [37][38][39][40][41][42][43] TADF LECs have been proposed. The host-guest TADF LECs generally showed higher device efficiencies than the neat-film TADF LECs due to reduced self-quenching and a lower possibility of triplet-triplet annihilation on the TADF guest molecules, which is a strong competing process against RISC.…”

Section: Introductionmentioning

confidence: 99%

White Light‐Emitting Electrochemical Cells Employing Phosphor‐Sensitized Thermally Activated Delayed Fluorescence to Approach All‐Phosphorescent Device Efficiencies

Chen

Huang

Luo

et al. 2023

Chemistry A European J

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Solid-state light-emitting electrochemical cells (LECs) show promising advantages of simple device architecture, low operation voltage, and insensitivity to the electrode work functions such that they have high potential in low-cost display and lighting applications. In this work, novel white LECs based on phosphor-sensitized thermally activated delayed fluorescence (TADF) are proposed. The emissive layer of these white LECs is composed of a blue-green phosphorescent host doped with a deep-red TADF guest. Efficient singlet-to-triplet intersystem crossing (ISC) on the phosphorescent host and the subsequent Förster energy transfer from the host triplet excitons to guest singlet excitons can make use of both singlet and triplet excitons on the host. With the good spectral overlap between the host emission and the guest absorption, 0.075 wt.% guest doping is sufficient to cause substantial energy transfer efficiency (ca. 40 %). In addition, such a low guest concentration also reduces the self-quenching effect and a high photoluminescence quantum yield of up to 84 % ensures high device efficiency. The phosphor-sensitized TADF white LECs indeed show a high external quantum efficiency of 9.6 %, which is comparable with all-phosphorescent white LECs. By employing diffusive substrates to extract the light trapped in the substrate, the device efficiency can be further improved by ca. 50 %. In the meantime, the intrinsic EL spectrum and device lifetime of the white LECs recover since the microcavity effect is destroyed. This work successfully demonstrates that the phosphor-sensitized TADF white LECs are potential candidates for efficient white light-emitting devices.

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“…[8][9][10][11][12][13] Recently, neat-film and host-guest LECs based on small molecules with thermally activated delayed fluorescence have also been demonstrated to exhibit good device efficiencies by recycling the triplet excitons via the efficient reverse intersystem crossing process. [14][15][16][17][18][19][20] Given the high potential for white LECs in lighting and display applications, they have been intensively studied since the first publication [21] and the device performance has been improved significantly. [22] In addition to employing efficient iTMCs, sophisticated device engineering technologies for white LECs have also been utilized to take full advantage of efficient materials.…”

Section: Introductionmentioning

confidence: 99%

Efficient Tandem White OLED/LEC Hybrid Devices

Luo

Hou

Wang

et al. 2023

Adv Materials Technologies

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Organic light‐emitting diodes (OLEDs) attract much research attention owing to their superior device characteristics in display and lighting applications. However, multi‐layered organic thin films deposited by thermal evaporation in a high‐vacuum chamber complicate the fabrication processes and increase the production costs. Alternatively, solution‐processable single‐layered light‐emitting electrochemical cells (LECs) possess easy fabrication and good device performance due to in situ electrochemical doping. To take advantages of both types of devices, the study proposes an efficient tandem white OLED/LEC hybrid device by stacking a red OLED on top of a blue LEC with a sophisticatedly designed charge‐generating layer (CGL). The proposed tandem device exhibits a high external quantum efficiency (EQE) of 21.53%, which is almost the sum of the EQEs of the two stacked devices. When fabricated on the diffusive substrate to recycle the trapped light in the substrate, the EQE can be further enhanced to reach 37.88%. Besides connecting the two stacked devices, the CGL improves the carrier balance of the blue LEC due to enhanced electron injection. This study demonstrates that the white tandem OLED/LEC hybrid device has a simpler device structure than all‐vacuum‐processed tandem OLEDs but it still delivers high device efficiency, revealing its potential in lighting applications.

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Intrinsically-ionic donor-acceptor molecules featuring thermally-activated delayed fluorescence for high-performance host-guest blue light-emitting electrochemical cells

Cited by 11 publications

References 64 publications

Dinuclearization strategy of cationic iridium(iii) complexes for efficient and stable flexible light-emitting electrochemical cells

Dinuclearization strategy of cationic iridium(iii) complexes for efficient and stable flexible light-emitting electrochemical cells

White Light‐Emitting Electrochemical Cells Employing Phosphor‐Sensitized Thermally Activated Delayed Fluorescence to Approach All‐Phosphorescent Device Efficiencies

Efficient Tandem White OLED/LEC Hybrid Devices

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