Efficient Green-Blue-Light-Emitting Cationic Iridium Complex for Light-Emitting Electrochemical Cells

Laboratory for Photonics and Interfaces, Institute of Chemical Sciences and Engineering, School of basic Sciences, Swiss Federal Institute of Technology, CH-1015 Lausanne, Switzerland.
Inorganic Chemistry (Impact Factor: 4.76). 12/2006; 45(23):9245-50. DOI: 10.1021/ic060495e
Source: PubMed


A highly luminescent novel cationic iridium complex [iridium bis(2-phenylpyridine)(4,4'-(dimethylamino)-2,2'-bipyridine)]PF6 was synthesized and characterized using NMR, UV-visible absorption, and emission spectroscopy and electrochemical methods. This complex displays intense photoluminescence maxima in the green-blue region of the visible spectrum and exhibits unprecedented phosphorescence quantum yields, 80 +/- 10% with an excited-state lifetime of 2.2 mus in a dichloromethane solution at 298 K. Single-layer light-emitting electrochemical cells with the charged complex as conducting and electroluminescent material sandwiched between indium-tin oxide and Ag electrodes were fabricated, which emit green-blue light with an onset voltage as low as 2.5 V. Density functional theory calculations were performed to provide insight into the electronic structure of the [iridium bis(2-phenylpyridine)(4,4'-(dimethylamino)-2,2'-bipyridine)]PF6 complex, comparing these results with those obtained for [iridium bis(2-phenylpyridine)(4,4'-tert-butyl-2,2'-bipyridine)]PF6.

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    • "Light-emitting electrochemical cells (LECs) have attracted increasing interest recently, mainly because they offer efficient light emission at low voltage from potentially easy-to-fabricate devices, but also because their complex and fascinating turn-on process has stirred a lot of debate regarding even its fundamental nature. Two main types of LECs exist: small-molecule based LECs, [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] and conjugated-polymer based LECs [15–34]. The former are commonly based on an ionic transition metal complex as the single-component active material, while the latter typically contain a three-component active material mixture , comprising a conjugated polymer (CP), an ion-solvating and ion-transporting material, and an alkaline salt. "
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    ABSTRACT: We present results from a systematic study on the influence of the conjugated polymer (CP) on the performance of planar light-emitting electrochemical cells (LECs) with a device structure of Au/{CP+poly(ethylene oxide) (PEO)+KCF3SO3}/Au. We have employed six different CPs, and we demonstrate that in order to attain a fast turn-on time and a strong light emission intensity, it is critical that the p-type doping (oxidation) potential of the CP is situated within the electrochemical stability window of the {PEO+KCF3SO3} electrolyte. We also find that a high ionic conductivity of the active material correlates with a small phase separation between the CP and the {PEO+KCF3SO3} electrolyte, and that a doping concentration of ∼0.1dopants/CP repeat unit is a generic feature of the progressing doping fronts in all investigated devices. Finally we report the first observation of a light emission zone positioned in close proximity to the positive anode in a CP-based LEC.
    Organic Electronics 10/2008; 9(5):699-710. DOI:10.1016/j.orgel.2008.05.010 · 3.83 Impact Factor
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    ABSTRACT: The aim of this chapter is to give an in-depth analysis of transition metal complexes that areuseful in conversion of solar energy into electricity, and in organic light emitting diodes. In thefirst part we discuss the historical background of sensitization phenomenon, operating principlesof dye-sensitized solar cells, tuning of photophysical and electrochemical properties of sensitizers,evolution of photovoltaic performance, present status and future prospects for dye-sensitized solarcells. In the second part, we elucidate the modulation of phosphorescent color and quantum yieldsin neutral, cationic, and anionic iridium complexes and their application in light emitting devices.
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    ABSTRACT: Ionic transition metal complexes (iTMCs) are receiving increased attention as materials capable of yielding efficient electroluminescent devices with air-stable electrodes. The operational characteristics of these devices are dominated by the presence of mobile ions that redistribute under an applied bias and assist in electronic charge injection. This article reviews recent efforts in the field of iTMC devices: i) to understand their physics, ii) to improve their efficiency, colour, turn-on time and lifetime, and iii) to expose their potential applications.
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