Higher efficiency in the end-use of energy requires substantial progress in lighting concepts. All the technologies under development are based on solid-state electroluminescent materials and belong to the general area of solid-state lighting (SSL). The two main technologies being developed in SSL are light-emitting diodes (LEDs) and organic light-emitting diodes (OLEDs), but in recent years, light-emitting electrochemical cells (LECs) have emerged as an alternative option. The luminescent materials in LECs are either luminescent polymers together with ionic salts or ionic species, such as ionic transition-metal complexes (iTMCs). Cyclometalated complexes of IrIII are by far the most utilized class of iTMCs in LECs. Herein, we show how these complexes can be prepared and discuss their unique electronic, photophysical, and photochemical properties. Finally, the progress in the performance of iTMCs based LECs, in terms of turn-on time, stability, efficiency, and color is presented.

Luminescent ionic transition-metal complexes for light-emitting electrochemical cells.

The recent developments in using iridium(III) complexes as phosphorescent emitters in electroluminescent devices, such as (white) organic light-emitting diodes and light-emitting electrochemical cells, are discussed. Additionally, applications in the emerging fields of molecular sensors, biolabeling, and photocatalysis are briefly evaluated. The basic strategies towards charged and non-charged iridium(III) complexes are summarized, and a wide range of assemblies is discussed. Small-molecule- and polymer-based materials are under intense investigation as emissive systems in electroluminescent devices, and special emphasis is placed on the latter with respect to synthesis, characterization, electro-optical properties, processing technologies, and performance.

Recent Developments in the Application of Phosphorescent Iridium(III) Complex Systems

Two blue-emitting cationic iridium complexes with 2-(1H-pyrazol-1-yl)pyridine (pzpy) as the ancillary ligands, namely, [Ir(ppy) 2 (pzpy)]PF 6 and [Ir(dfppy)2(pzpy)]PF6 (ppy is 2-phenylpyridine, dfppy is 2-(2,4-difluorophenyl) pyridine, and PF 6 -is hexafluorophosphate), have been prepared, and their photophysical and electrochemical properties have been investigated. In CH 3 CN solutions, [Ir(ppy) 2 (pzpy)]PF 6 emits blue-green light (475 nm), which is blue-shifted by more than 100 nm with respect to the typical cationic iridium complex [Ir(ppy)2(dtb-bpy)]PF6 (dtb-bpy is 4,4'-di-tert-butyl-2,2'-bipyridine); [Ir(dfppy)2(pzpy)]PF 6 with fluorine-substituted cyclometalated ligands shows further blue-shifted light emission (451 nm). Quantum chemical calculations reveal that the emissions are mainly from the ligand-centered 3 π-π * states of the cyclometalated ligands (ppy or dfppy). Light-emitting electrochemical cells (LECs) based on [Ir(ppy) 2 (pzpy)]PF 6 gave green-blue electroluminescence (486 nm) and had a relatively high efficiency of 4.3 cd A -1 when an ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate was added into the light-emitting layer. LECs based on [Ir(dfppy)2(pzpy)]PF 6 gave blue electroluminescence (460 nm) with CIE (Commission Internationale de L'Eclairage) coordinates of (0.20, 0.28), which is the bluest light emission for iTMCs-based LECs reported so far. Our work suggests that using diimine ancillary ligands involving electron-donating nitrogen atoms (like pzpy) is an efficient strategy to turn the light emission of cationic iridium complexes to the blue region.

Blue-Emitting Cationic Iridium Complexes with 2-(1H-Pyrazol-1-yl)pyridine as the Ancillary Ligand for Efficient Light-Emitting Electrochemical Cells

Cationic blue-emitting complexes with (2,4-difluoro)phenylpyridine and different 1,2,3-triazole ligands are synthesized with different counterions. The influence of the substituents on the triazole ligand is investigated as well as the influence of the counterions. The substituents do not change the emission energy but, in some cases, slightly modify the excited-state lifetimes and the emission quantum yields. The excited-state lifetimes, in apolar solvents, are slightly dependent on the nature of the counterion. A crystal structure of one of the compounds confirms the geometry and symmetry postulated on the basis of the other spectroscopic data. Light-emitting electrochemical cell devices are prepared and the recorded emission is the bluest with the fastest response time ever reported for iridium complexes.

Positively Charged Iridium(III) Triazole Derivatives as Blue Emitters for Light-Emitting Electrochemical Cells

Ionic iridium(III) complexes are emerging with great promise for organic electronic devices, owing to their unique features such as ease of molecular design and synthesis, excellent photophysical properties, superior redox stability, and highly efficient emissions of virtually all colors. Here, recent progress on new material design, regarding photo- and electroluminescence is highlighted, including several interesting topics such as: i) color-tuning strategies of cationic iridium(III) complexes, ii) widespread utilization in phosphorescent light-emitting devices fabricated by not only solution processes but also vacuum evaporation deposition, and iii) potential applications in data record, storage, and sercurity. Results on anionic iridium(III) complexes and “soft salts” are also discussed, indicating a new related subject. Finally, a brief outlook is suggested, pointing out that ionic iridium(III) complexes should play a more significant role in future organic electronic materials technology.

Recent Progress in Ionic Iridium(III) Complexes for Organic Electronic Devices

A new, but archetypal compound [Ir(ppy-F2)2Me4phen]PF6, where ppy-F2 is 2-(2′,4′-fluorophenyl)pyridine and Me4phen is 3,4,7,8-tetramethyl-1,10-phenanthroline, was synthesized and used to prepare a solid-state light-emitting electrochemical cell (LEEC). This complex emits blue light with a maximum at 476 nm when photoexcited in a thin film, with a photoluminescence quantum yield of 52%. It yields an efficient single-component solid-state electroluminescence device with a current efficiency reaching 5.5 cd A−1 and a maximum power efficiency of 5.8 Lm Watt−1. However, the electroluminescence spectrum is shifted with respect to the photoluminescence spectrum by 80 nm resulting in the emission of green light. We demonstrate that this unexpected shift in emission spectrum does not originate from the mode of excitation, nor from the presence of large concentrations of ions, but is related to the concentration of the ionic transition metal complex in the thin film. The origin of the concentration-dependent emission is extensively commented on and argued to be related to the population of either 3LC π–π* or 3MLCT triplet states, in diluted and concentrated films, respectively. Using quantum chemical calculations we demonstrate that three low-energy triplet states are present with only 0.1 eV difference in energy and that their associated emission wavelengths differ by as much as 60 nm from each other.

Origin of the large spectral shift in electroluminescence in a blue light emitting cationic iridium(III) complex

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Stephanie Cheylan

Author Tools

Chat about Author

Papers

Origin of the large spectral shift in electroluminescence in a blue light emitting cationic iridium(III) complex