Small Molecules in Light‐Emitting Electrochemical Cells: Promising Light‐Emitting Materials

Shanmugasundaram, Kanagaraj; Puthanveedu, Archana; Choe, Youngson

doi:10.1002/adfm.201907126

Cited by 64 publications

(67 citation statements)

References 202 publications

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“…The typical structures of this class of complexes are shown in Scheme 4. For the MnX 4 2 -type ones (15)(16)(17)(18)(19)(20)(21), various ammonium-based organic cations have been adopted as counterions. These complexes also show intensive green phosphorescence with the decay time in microseconds ( Table 2).…”

Section: Manganese(ii) Complexes Based On Ammonium Saltsmentioning

confidence: 99%

Phosphorescent Manganese(II) Complexes and Their Emerging Applications

Tao

Liu

Wong

2020

Advanced Optical Materials

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light-emitting device (OLED) in 1998, [1] phosphorescent transition-metal complexes, especially for noble metal-based ones (e.g., iridium(III), platinum(II), etc.) as triplet emitters toward highly efficient organic electroluminescence, have aroused extensive attention. [15-21] Owing to strong spin-orbit coupling effect, these complexes may use both singlet and triplet excitons to greatly enhance the efficiency of OLED, breaking the upper limit of the conventional fluorescent device efficiency. Due to their unique properties of excited states, they also have extended their applications in other fields, for instance, catalysis, organic solar cells, organic memory devices, biological sensing and imaging, photodynamic therapy, information recording, and security protection, etc. [22-27] Although extensive works have been done to the design and preparation of phosphorescent materials based on noble metals, these noble metals usually have some disadvantages (such as high cost and low abundance in nature), thereby limiting their practical applications. The relatively abundant and cheap PTMCs of low toxicity have drawn considerable interests very recently. [4,23,24,28-31] Many kinds of non-noble metal-based PTMCs such as copper(I), tungsten(VI), and manganese(II) complexes have emerged rapidly. [4,23-25,28-31] Phosphorescent manganese(II) complexes show great potentials in many applications, due to their features including highly efficient phosphorescence, flexible design in molecular structure, ease of synthesis, and rich physical properties (e.g., triboluminescence, stimuli-responsivity, etc.). [24,25a,32-36] Compared with the noble metals, manganese element with an atomic number of 25 has abundant reserves, is environmentally friendly and inexpensive. Moreover, it has richer valence and coordination mode, which has been widely used in the fields of catalysis, ferroelectric, and magnetic materials. [37-39] Among the various valence states of manganese ion, the divalent manganese ion having a 3d 5 electron configuration has a 4 T 1 − 6 A 1 radiative transition closely related to the crystal field strength. The crystal field strength in the metal complex highly depends on the chemical structure of the ligand and the coordination number. These features make the manganese(II) complexes having rich photophysical properties. By regulating the ligand structure, the organic counterion and the coordination number of the manganese(II) complex, the green, yellow, orange, red, or even near-infrared phosphorescence can be achieved. [23-25,36,40] It Phosphorescent manganese(II) complexes are emerging as a new generation of phosphorescent materials showing great potentials in many applications, owing to their unique features including highly efficient phosphorescence, diverse structural/molecular design, and ease of synthesis, structural diversity, rich physical properties (e.g., triboluminescence, stimuli-responsivity, etc.), high abundance, and low cost. The research on phosphorescent manganese(II) complexes is just in its infancy...

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Section: Manganese(ii) Complexes Based On Ammonium Saltsmentioning

confidence: 99%

Phosphorescent Manganese(II) Complexes and Their Emerging Applications

Tao

Liu

Wong

2020

Advanced Optical Materials

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“…A wide variety of emitting materials, [ 2,6,7 ] such as fluorescent polymers and small molecules, [ 1,8,9 ] phosphorescent ionic transition‐metal complexes, [ 10–14 ] thermally‐activated delayed fluorescence (TADF) molecules, [ 15–17 ] quantum dots, [ 18 ] and perovskite, [ 18–20 ] have been used for LECs. With these emitting materials, red to blue and white LECs have been fabricated.…”

Section: Introductionmentioning

confidence: 99%

“…With these emitting materials, red to blue and white LECs have been fabricated. [ 2–4,8–14,18 ] However, blue LECs have shown inferior performances, [ 12,13 ] which has remained a formidable challenge for the fabrication of white LECs for lighting applications. [ 2–4 ] Color stability, efficiency, brightness and operational stability are four critical parameters to evaluate blue LECs for real‐world applications.…”

Section: Introductionmentioning

confidence: 99%

Color‐Stable, Efficient, and Bright Blue Light‐Emitting Electrochemical Cell Using Ionic Exciplex Host

Bai

Meng

Wang

et al. 2020

Adv Funct Materials

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The lack of high-performance blue light-emitting electrochemical cells (LECs) has remained a formidable challenge for fabricating white LECs for lighting applications. Here, a ionic exciplex host is used for color-stable, efficient, and bright blue LECs by taking advantage of its facilitated carrier injection, bipolar charge-transport, and efficient energy transfer to the guest dopant. A cationic donor molecule, 1-(3-(3,6-di-tert-butyl-9H-carbazol-9-yl)phenyl)-3-methyl-1H-imidazol-3-ium hexafluorophosphate (tbuCAZ-ImMePF 6), and a cationic acceptor molecule, 1-(3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-3-ethyl-1Himidazol-3-ium hexafluorophosphate (TRZ-ImEtPF 6), are developed to form the ionic exciplex host. The mixed film of tbuCAZ-ImMePF 6 and TRZ-ImEtPF 6 affords blue exciplex with fast reverse intersystem crossing and thermally activated delayed fluorescence. For the film doped with a blue-emitting iridium complex, energy is efficiently transferred from the exciplex to the complex. Host-guest LECs using the doped film as the active layer show stable blue emission color and high current efficiencies of up to 25.8 cd A −1. More importantly, they attain simultaneously high efficiency and high brightness (14.1/17.4/16.8 cd A −1 at 705/872/1680 cd m −2), which are the most efficient and bright host-guest blue LECs reported so far. The primary host-guest LEC also exhibits promising operational stability. The work reveals that the use of an ionic exciplex host is a promising avenue toward high-performance blue LECs.

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“…The simplicity of LECs and their processing from solution has motivated that the research activity on LECs has considerably increased in the last years. [6][7][8][9][10] Much interest has centred upon LECs incorporating ionic transition-metal complexes (iTMCs), which are inherently more efficient than those based upon charged light-emitting polymers as the emission is based on phosphorescence rather than on uorescence. [11][12][13] The colourtuning of iTMC-based LECs is well-established in the case of iridium complexes, although the use of this element makes again the sustainability questionable.…”

Section: Introductionmentioning

confidence: 99%