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Polymer light-emitting electrochemical cells (LECs) are inherently dependent on a suitable electrolyte for proper function. Here, we design and synthesize a series of alkyl carbonate-capped star-branched oligoether-based electrolytes with large electrochemical stability windows, facile ion release, and high compatibility with common light-emitting materials. LECs based on such designed electrolytes feature fast turn-on, a long operational lifetime of 1400 h at >100 cd m-2 and a record-high power conversion efficiency of 18.1 lm W-1, when equipped with an external outcoupling film. [ABSTRACT FROM AUTHOR]

The electrolyte is a key componentin light-emitting electrochemicalcells (LECs), as it facilitates in situelectrochemicaldoping and associated attractive device features. LiCF3SO3dissolved in hydroxyl-capped trimethylolpropane ethoxylate(TMPE-OH) constitutes an electrolyte with which we have attained highstability and efficiency for polymer LECs, but the turn-on time ofsuch devices is unfortunately slow. By replacing hydroxyl with methoxyas the TMPE end-group, we produced LECs with a desired combinationof high efficiency, good stability, and fast turn-on time. Specifically,we showed that the turn-on time to high luminance (300 cd/m2) at a current density of 7.7 mA/cm2is lowered from 1740to 16 s, that the efficiency is improved by ∼20%, and thatthe other device properties are either maintained or improved. Ina parallel modeling and experimental effort, we demonstrated thatthe faster kinetics following the shift in the TMPE end-group is attributedto a marked decrease in the level of both inter- and intramolecularinteractions of the electrolyte, as manifested in a lowered electrolyteviscosity, faster ion transport, and more facile ion release duringdoping. [ABSTRACT FROM AUTHOR]

Inlight-emitting electrochemical cells, the lifetime of the deviceis intrinsically linked to the stability of the phosphorescent emitter.In this study, we present a series of ionic iridium(III) emittersbased on cyclometalating phenylpyridine ligands whose fluorine substituentsare varied in terms of position and number. Importantly, despite thesestructural modifications, the emitters exhibit virtually identicalelectrochemical and spectroscopic properties, which allows for propercomparison in functional devices. Quantum-chemical calculations supportthe properties measured in solution and suggest great similaritiesregarding the electronic structures of the emitters. In electroluminescentdevices, the initial luminance, efficiency, and efficacy are alsorelatively unaffected throughout the series. However, a shorter devicelifetime is obtained upon increasing the fluorine content of the emitter,which suggests drawbacks of such electron-withdrawing substituentsfor the design of ionic iridium(III) emitters. [ABSTRACT FROM AUTHOR]

Blue-green-emitting cationic iridium complex with high luminescent efficiencies in both solutions and solid-states are essential for high-performance white light-emitting electrochemical cells (LECs). We report here an efficient blue-green-emitting cationic iridium complex [Ir(dfppz)2(tp-pyim)]PF6, using 1-(2,4-difluorophenyl)-1H-pyrazole (dfppz) as the cyclometalated ligand and 2-(1-(4-tritylphenyl)-1H-imidazol-2-yl)pyridine (tp-pyim) as the ancillary ligand. [Ir(dfppz)2(tp-pyim)]PF6emits efficient blue-green light with a luminescent quantum yield of 0.54 in CH3CN solution. Because of the sterically bulky group 4-tritylphenyl that is attached to the ancillary ligand, the intermolecular interaction and excited-state self-quenching of [Ir(dfppz)2(tp-pyim)]PF6in solid states is significantly suppressed. Theoretical calculations reveal that the emission from [Ir(dfppz)2(tp-pyim)]PF6has both metal-to-ligand charge-transfer and ligand-centered 3π−π* character. LECs based on [Ir(dfppz)2(tp-pyim)]PF6show highly efficient blue-green electroluminescence with peak current efficiency, external quantum efficiency, and power efficiency of 18.3 cd A−1, 7.6%, and 18.0 lm W−1, respectively. White LECs based on [Ir(dfppz)2(tp-pyim)]PF6give warm-white light, with Commission Internationale de L’Eclairage coordinates of (0.37, 0.41), a color-rendering index up to 80, and a peak power efficiency of 11.2 lm W−1. [ABSTRACT FROM AUTHOR]

Fixed-junction light-emitting electrochemical cells (LECs) using ion-pair monomers (IPMs) have been shown to be promising. Here we present several novel polymerizable ionic liquids that combine the advantages of ionic liquids with the fixed-junction functionality of IPMs. We show significantly improved performance over earlier IPM-based fixed-junction LECs. [ABSTRACT FROM AUTHOR]