Luminescent Iridium Complexes Used in Light-Emitting Electrochemical Cells (LEECs)

Henwood, Adam Francis; Zysman‐Colman, Eli

doi:10.1007/978-3-319-59304-3_2

Cited by 11 publications

(7 citation statements)

References 57 publications

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“…The value of t 1/2 extrapolated for [3][PF 6 ] is among the best values available in the bibliography for LECs. In a recent review, 11 Henwood and Zysman-Colman concluded that the most stable emitter reported to date under the same pulsed current operation of 100 A m -2 was presented by Tordera et al, 59 who described a LEC device based on an imidazole-including complex 6 ]. The device stability obtained when using [3][PF 6 ] is longer (t 1/2 = 2700 vs. 2000 h), the turn-on time is shorter (6.9 vs. 45 s), the maximum luminance is higher (904 vs. 684 cd m −2 ), and the maximum current efficiency is also higher (9.2 vs 6.5 cd A…”

Section: Theoretical Calculationsmentioning

confidence: 95%

“…A wide range of organic materials has been used in the manufacture of LECs. 7,8,9,10,11 However, the best efficiencies have been achieved with ionic transition-metal complexes (iTMCs), 12,13,14,15 and, in particular, with iridium(III) complexes due to their efficient spin-orbit coupling, which ideally allows to harvest 100% of the excitons generated in the device.…”

Section: Introductionmentioning

confidence: 99%

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Highly Stable and Efficient Light-Emitting Electrochemical Cells Based on Cationic Iridium Complexes Bearing Arylazole Ancillary Ligands

et al. 2017

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A series of bis-cyclometalated iridium(III) complexes of general formula [Ir(ppy)2(N∧N)][PF6] (ppy– = 2-phenylpyridinate; N∧N = 2-(1H-imidazol-2-yl)pyridine (1), 2-(2-pyridyl)benzimidazole (2), 1-methyl-2-pyridin-2-yl-1H-benzimidazole (3), 2-(4′-thiazolyl)benzimidazole (4), 1-methyl-2-(4′-thiazolyl)benzimidazole (5)) is reported, and their use as electroluminescent materials in light-emitting electrochemical cell (LEC) devices is investigated. [2][PF6] and [3][PF6] are orange emitters with intense unstructured emission around 590 nm in acetonitrile solution. [1][PF6], [4][PF6], and [5][PF6] are green weak emitters with structured emission bands peaking around 500 nm. The different photophysical properties are due to the effect that the chemical structure of the ancillary ligand has on the nature of the emitting triplet state. Whereas the benzimidazole unit stabilizes the LUMO and gives rise to a 3MLCT/3LLCT emitting triplet in [2][PF6] and [3][PF6], the presence of the thiazolyl ring produces the opposite effect in [4][PF6] and [5][PF6] and the emitting state has a predominant 3LC character. Complexes with 3MLCT/3LLCT emitting triplets give rise to LEC devices with luminance values 1 order higher than those of complexes with 3LC emitting states. Protecting the imidazole N–H bond with a methyl group, as in complexes [3][PF6] and [5][PF6], shows that the emissive properties become more stable. [3][PF6] leads to outstanding LECs with simultaneously high luminance (904 cd m–2), efficiency (9.15 cd A–1), and stability (lifetime over 2500 h).

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Section: Theoretical Calculationsmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Highly Stable and Efficient Light-Emitting Electrochemical Cells Based on Cationic Iridium Complexes Bearing Arylazole Ancillary Ligands

et al. 2017

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“…Although chromonic systems are generally characterized by planar structures surrounded by peripheral solubilizing and/or ionic groups, or ionic square planar geometry metal complexes having hydrophilic counterions, Yadav et al showed for the first time self-assembly into chromonic-like mesophases of bulky octahedral luminescent Ir(III) complexes [129] (complexes Ir_3a-c in Figure 15). Even if they belong to a family of Ir(III) emitters of general formula [(ppy) 2 Ir(N^N)] + Xwhere ppy is 2-phenylpyridine and N^N is 2,2 ′ -bipyridine or 1,10-phenanthroline, highly researched for practical for applications in Light Emitting Electrochemical Cells (LEECs) [130,131], only by changing the counterions with carboxylates of various alkyl chains, water solubility, and self-assembling ability into chromoniclike liquid crystalline phases was induced [132] (complexes Ir_4 in Figure 15).…”

Section: Chromonic or Chromonic-like Coordination Complexesmentioning

confidence: 99%

Luminescent Supramolecular Nano- or Microstructures Formed in Aqueous Media by Amphiphile-Noble Metal Complexes

Cretu

Maiuolo

Lombardo

et al. 2020

Journal of Nanomaterials

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The involvement of metal ions within the self-assembly spontaneously occurring in surfactant-based systems gives additional and interesting features. The electronic states of the metal, together with the bonds that can be established with the organic amphiphilic counterpart, are the factors triggering new photophysical properties. Moreover, the availability of stimuli-responsive supramolecular amphiphile assemblies, able to disassemble in a back-process, provides reversible switching particularly useful in novel approaches and applications giving rise to truly smart materials. In particular, small amphiphiles with an inner distribution, within their molecular architecture, of various polar and apolar functional groups, can give a wide variety of interactions and therefore enriched self-assemblies. If it is joined with the opportune presence and localization of noble metals, whose chemical and photophysical properties are undiscussed, then very interesting materials can be obtained. In this minireview, the basic concepts on self-assembly of small amphiphilic molecules with noble metals are shown with particular reference to the photophysical properties aiming at furnishing to the reader a panoramic view of these exciting problematics. In this respect, the following will be shown: (i) the principles of self-assembly of amphiphiles that involve noble metals, (ii) examples of amphiphiles and amphiphile-noble metal systems as representatives of systems with enhanced photophysical properties, and (iii) final comments and perspectives with some examples of modern applications.

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“…Along these lines, the major thrust of this work is the unveiling of the impact of the selfheating on the chromaticity and efficiency of LECs using a benchmark nanographenei.e., hexaperihexabenzocoronene or 1 32 as an emerging class of emitters with outstanding device performance. Since LECs show a high versatility with respect to the type of emitters, 4,23,[33][34][35][36][37][38][39] the impact of self-heating can, indeed, be considered as universal. For instance, Figure S1 displays the working pixel temperature of 40-50 °C LECs with d 6 -/d 10 -complexes and small molecules operating at pulsed 100 mA/cm 2 , 7,24,40 while Edman's group has recently showed that polymer-LECs reach 50 °C at 50 mA/cm 2 .…”

Section: Introductionmentioning

confidence: 99%

Revealing the Impact of Heat Generation Using Nanographene-Based Light-Emitting Electrochemical Cells

Fresta

Dosso

Cabanillas‐González

et al. 2020

ACS Appl. Mater. Interfaces

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Self-heating in light-emitting electrochemical cells (LECs) has been long overlooked, while it has a significant impact on i) device chromaticity by changing the electroluminescent band shape, ii) device efficiency due to thermal quenching and exciton dissociation reducing the external quantum efficiency (EQE), and iii) device stability due to thermal quenching of excitons and formation of doped species, phase separation, and collapse of the intrinsic emitting zone. Herein, we reveal, for the first time, a direct relationship between self-heating and the early changes of the device chromaticity as well as the magnitude of the error comparing theoretical/experimental EQEs -i.e., overestimation error of ca. 35 % at usual pixel working temperatures of around 50 °C. This has been realized in LECs using a benchmark nanographene i.e., a substituted hexa-peri-hexabenzocoronene -as an emerging class of emitters with outstanding device performance compared to the prior-art of small molecule LECs -e.g., luminances of 345 cd/m 2 and EQEs of 0.35%. As such, this work is a fundamental contribution highlighting how self-heating is a critical limitation towards the optimization and wide use of LECs.

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Luminescent Iridium Complexes Used in Light-Emitting Electrochemical Cells (LEECs)

Cited by 11 publications

References 57 publications

Highly Stable and Efficient Light-Emitting Electrochemical Cells Based on Cationic Iridium Complexes Bearing Arylazole Ancillary Ligands

Highly Stable and Efficient Light-Emitting Electrochemical Cells Based on Cationic Iridium Complexes Bearing Arylazole Ancillary Ligands

Luminescent Supramolecular Nano- or Microstructures Formed in Aqueous Media by Amphiphile-Noble Metal Complexes

Revealing the Impact of Heat Generation Using Nanographene-Based Light-Emitting Electrochemical Cells

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