Multinuclear Iridium Complex Encapsulated by Oligocarbazole Dendrons for Enhanced Nondoped Device Efficiency

Wang, Yang; Wang, Shumeng; Ding, Junqiao; Wang, Lixiang

doi:10.1021/acsomega.8b02579

Cited by 4 publications

(1 citation statement)

References 33 publications

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“…Nowadays, a series of dendrimers have been successfully demonstrated, whose emission colors can range from blue to red. − However, we observe that the turn-on voltage, especially for blue-emitting ones, is still far away from the driving voltage theoretical limit ( E g / e : corresponds to the optical bandgap divided by the electron charge) . To solve such a problem, we have, for the first time, proposed dendron engineering in self-host blue phosphorescent dendrimers to develop power-efficient nondoped OLEDs that can be drived at low voltage which is adjacent the theoretical limit.…”

Section: Introductionmentioning

confidence: 99%

Solution-Processible Blue Fluorescent Dendrimers with Carbazole/Diphenylamine Hybrid Dendrons for Power-Efficient Organic Light-Emitting Diodes

et al. 2019

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Two blue fluorescent dendrimers named PVAC2 and PVACA have been newly synthesized and investigated, where the carbazole/diphenylamine hybrid dendron is adopted instead of oligocarbazole. Compared with the reference dendrimer PVCt3, the emission maxima of PVAC2 and PVACA are found to be red-shifted accompanied by a slight reduction of the photoluminescence quantum yield in films. Most importantly, the highest occupied molecular orbital level is elevated from −5.35 eV of PVCt3 to −5.20 eV of PVAC2 and −4.95 eV of PVACA. Because of the favored hole injection, the turn-on voltage is accordingly decreased from 3.6 to 3.2 and 2.6 V. The value of PVACA is even lower than the theoretical limit of 2.78 V. In addition, PVAC2 exhibited the best nondoped device performance, showing a nearly doubled power efficiency of 4.80 lm/W relative to PVCt3 (2.37 lm/W). The results clearly indicate that dendron engineering is also a promising strategy to develop solution-processible blue fluorescent dendrimers capable of being used for power-efficient organic light-emitting diodes.

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Section: Introductionmentioning

confidence: 99%

Solution-Processible Blue Fluorescent Dendrimers with Carbazole/Diphenylamine Hybrid Dendrons for Power-Efficient Organic Light-Emitting Diodes

et al. 2019

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Phosphine Oxide Linkage Manipulating Trinuclear Iridium(III) Complex for High‐Efficiency Bilayer Nondoped Organic Light‐Emitting Diodes

Wei

Zhang

Kan

et al. 2020

Advanced Optical Materials

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A conventional approach to construct efficient PH neat films is combining host and phosphor moieties in single molecules. [7] In this case, phosphorescent emitting cores were encapsulated in host-featured peripheral carrier-transporting groups, [8] dendrons [9] or polymeric skeletons, [10] therefore protected from intermolecular interaction induced collisional quenching by steric effect of functional groups. Wang et al. reported a square-planar Pt 3+ complex, whose vacuum-evaporated non-doped PH OLED (PHOLED) achieved a maximum η EQE of 31%. [11] However, only few solution-processed non-doped PHOLEDs can realize η EQE close to 20%, among which Wang et al. reported a small-molecular Ir 3+ complex with an impressive η EQE of 18.5%. [12] Therefore, the separation by peripheral groups seems not essential for constructing high-efficiency phosphors for non-doped devices. In opposite, the highest occupied (HOMO) and the lowest unoccupied molecular orbitals (LUMO) of the peripheral groups should be deeper and shallower than those of emitting cores, respectively, to confine charge and exciton on the latter, therefore, complicated stacks involving in multiple hole (HTL) and electron transporting layers (ETL) were commonly adopted. [13] Furthermore, energy transfer from peripheral groups to emitting cores leads to energy loss, decreasing the power efficiency of the devices. [14] Actually, Wang and Ding et al. have demonstrated the self-host feature of aliphatic chain-linked multinuclear Ir 3+ complexes. [15] Nevertheless, since triplet quenching is still mainly induced by molecular collision, optimizing intermolecular interactions is still crucial for developing high-efficiency non-doped PHOLEDs. Herein, we demonstrate another effective "linkage manipulation" strategy to develop solution-processable phosphors. An Ir 3+ complex Ir(PBI) 3 (PBI = 1,N-diphenyl benzimidazole) is employed as phosphorescent core, which was linked with triphenylphosphine oxide (TPPO) to form mononuclear Ir(PBI) 2 PBIPO, binuclear [Ir(PBI) 2 ] 2 DPBIPO, and trinuclear [Ir(PBI) 2 ] 3 TPBIPO. The incorporation of TPPO linkage hardly changes single-molecular emission profiles and peak wavelengths, but induces the gradual increase of photoluminescence quantum yield (PLQY, η PL), from 76% of TPPO-free Ir(PBI) 3 to 92% of [Ir(PBI) 2 ] 3 TPBIPO, corresponding to a 50% improved PH rate constant. More importantly, tetrahedral configuration of TPPO linkage destroys the symmetry of Ir 3+ cores in the multinuclear complexes, therefore effectively suppresses triplet quenching. [Ir(PBI) 2 ] 3 TPBIPO Developing high-efficiency nondoped phosphorescence (PH) organic lightemitting diodes (OLEDs) by solution processing is still a big challenge, due to high demand on quenching suppression ability of phosphors. Here, phosphine oxide (PO) linkage is incorporated between Ir 3+ complexed cores of a trinuclear phosphorescent emitter named [Ir(PBI) 2 ] 3 TPBIPO. The emission spectra of single-molecular [Ir(PBI) 2 ] 3 TPBIPO is identical to its mononuclear congeners, but its ...

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Triphenylamine-based trinuclear Pt(II) complexes for solution-processed OLEDs displaying efficient pure yellow and red emissions

Sun

Liu

Guo

et al. 2021

Organic Electronics

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Multinuclear Iridium Complex Encapsulated by Oligocarbazole Dendrons for Enhanced Nondoped Device Efficiency

Cited by 4 publications

References 33 publications

Solution-Processible Blue Fluorescent Dendrimers with Carbazole/Diphenylamine Hybrid Dendrons for Power-Efficient Organic Light-Emitting Diodes

Solution-Processible Blue Fluorescent Dendrimers with Carbazole/Diphenylamine Hybrid Dendrons for Power-Efficient Organic Light-Emitting Diodes

Phosphine Oxide Linkage Manipulating Trinuclear Iridium(III) Complex for High‐Efficiency Bilayer Nondoped Organic Light‐Emitting Diodes

Triphenylamine-based trinuclear Pt(II) complexes for solution-processed OLEDs displaying efficient pure yellow and red emissions

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