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: 4.79). 12/2006; 45(23):9245-50. DOI: 10.1021/ic060495e
Source: PubMed

ABSTRACT 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.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Two dendrimers, D1 and D2, containing the cationic iridium complexes (C1 and C2) as cores and truxene-functionalized chromophores as the branches, have been developed by a convergent synthetic strategy. The cationic complexes employ 3-(pyridin-2-yl)-1H-1,2,4-triazole and 2-(pyridin-2-yl)-benzimidazole derivatives as the ancillary ligands. To avoid the change in emission colour arising from the iridium complex, the conjugation between the dendron and the ligand is decoupled by separating them using the alkyl chain. An investigation of their photoluminescent features reveals that efficient energy transfer happens from the dendrons to the core in the solid state. Likewise, the charged dendritic structure is demonstrated to be an efficient method to improve the compatibility between the polar charged iridium complexes and typical hydrophobic hosts with the additional benefit of excellent solution processability. Both dendrimers exhibit strong solvatochromic behaviours in solvents and exclusive green and yellow-orange light in the solid state.
    Australian Journal of Chemistry 10/2011; 64(9):1211-1220. · 1.64 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: An elaborated theoretical investigation on the optical and electronic properties of three fluorene-based platinum(II) and iridium(III) cyclometalated complexes Pt-a, Ir-a and Ir-b is reported. The geometric and electronic structures of the complexes in the ground state are studied with density functional theory and Hartree Fock approaches, while the lowest triplet excited states are optimized by singles configuration interaction (CIS) methods. At the time-dependent density functional theory (TD-DFT) level, molecular absorption and emission properties were calculated on the basis of optimized ground- and excited-state geometries, respectively. The computational results show that the appearance of triphenylamino (TPA) moiety at the 9-position of fluorene ring favors the hole-creation and leads to red-shifts of absorption and emission spectra. Moreover, Pt-a and Ir-b are nice hole-transporting materials whereas Ir-a has good charge-transfer balance, which render them useful for the realization of efficient OLEDs (Organic Light-Emitting Diodes).
    Chinese Journal of Chemistry 10/2012; 30(10). · 0.92 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Time-dependent density functional theory (TD-DFT) with the quadratic response technique is applied to the tris(8-hydroxyquinoline) aluminum complex (Alq3) to calculate spin–orbit coupling (SOC) effects and the main mechanism of the Alq3 phosphorescence. This compound exhibits weak phosphorescence which provides additional emission in organic light emitting diodes (OLEDs) besides the main fluorescence band. The phosphorescence affords to overcome the efficiency limit imposed by the formation of triplet excitons in the emissive layer of OLEDs. The zero-field splitting (ZFS) parameters are also calculated taking into account the spin–spin coupling in the first-order perturbation theory and the SOC in the second order. On the basis of the results obtained, we propose that an efficient spin-polarized injection and transport in long channels of Alq3, which have been recently achieved with new hybrid organic–inorganic interfaces, can proceed with the triplet electronic state admixture to the charge carriers. Our results also indicate that weak spin–orbit coupling may be responsible for the room-temperature magneto-resistance at the ferromagnetic–Alq3 interfaces and the spin-dependent charge transport.
    The Journal of Physical Chemistry C 02/2013; 117(7):3446–3455. · 4.84 Impact Factor