Archetype cationic iridium complexes and their use in solid-state light-emitting electrochemical cells

Rubén D. Costa, Enrique Ortí, Henk J. Bolink, Stefan Graber, Silvia Schaffner, Markus Neuburger, Catherine E. Housecroft, Edwin C. Constable

Research output: Contribution to journalArticlepeer-review

214 Citations (Scopus)

Abstract

The archetype ionic transition-metal complexes (iTMCs) [lr(ppy) 2(bpy)][PF6] and [lr(ppy)2(phen)][PF 6], where Hppy = 2-phenylpyridine, bpy = 2,2′bipyridine, and phen = 1,10-phenanthroline, are used as the primary active components in light-emitting electrochemical cells (LECs). Solution and solid-state photophysical properties are reported for both complexes and are interpreted with the help of density functional theory calculations. LEC devices based on these archetype complexes exhibit long turn-on times (70 and 160h, respectively) and low external quantum efficiencies (∼2%) when the complex is used as a pure film. The long turn-on times are attributed to the low mobility of the counterions. The performance of the devices dramatically improves when small amounts of ionic liquids (ILs) are added to the Ir-iTMC: the turn-on time improves drastically (from hours to minutes) and the device current and power efficiency increase by almost one order of magnitude. However, the improvement of the turn-on time is unfortunately accompanied by a decrease in the stability of the device from 700 h to a few hours. After a careful study of the lr-iTMC:IL molar ratios, an optimum between turn-on time and stability is found at a ratio of 4:1. The performance of the optimized devices using these rather simple complexes is among the best reported to date. This holds great promise for devices that use specially-designed iTMCs and demonstrates the prospect for LECs as low-cost light sources.

Original languageEnglish
Pages (from-to)3456-3463
Number of pages8
JournalAdvanced Functional Materials
Volume19
Issue number21
DOIs
Publication statusPublished - 2009 Nov 9
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

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