Sky-blue-emitting cationic iridium complexes with carbazole-type counter-anions and their use for efficient solution-processed organic light-emitting diodes

The control of counter-anion is a facile approach to tune the overall properties of cationic iridium complexes for optoelectronic applications. Here, we report for the first time the use of electron-rich carbazole-type counter-anions in cationic iridium complexes and the use of such complexes as dopants in solution-processed organic light-emitting diodes (OLEDs). PF6-, 4-(9H-carbazol-9-yl)benzenesulfonate (CAZ-SO3-), and 4-(9'H-[9,3':6',9''-tercarbazol]-9'-yl)benzenesulfonate (TCAZ-SO3-) have been employed as the counter-anions of sky-blue-emitting complexes R, 1 and 2, respectively. The carbazole-type counter-anions do not largely disturb the phosphorescence of the cations and the complexes show similar emission properties in solution and films. The close proximity of the carbazole-type anions to the phosphorescent cations allows efficient energy-transfer from the former to the latter in films. When used as dopants in solution-processed OLEDs, complexes 1 and 2 show higher performances than complex R because the hole-trapping effects of the carbazole-type counter-anions largely improve the carrier-recombination balance in the emissive layers. In particular, the double-layer sky-blue device based on complex 2 with strong hole-trapping by TCAZ-SO3- affords a high peak current efficiency of 27.1 cd A-1. The work reveals that electron-rich carbazole-type anions are promising counter-anions for cationic iridium complexes toward optoelectronic applications.

A theoretical study on the electronic structure and phosphorescence properties of two series of iridium(iii) complexes with a four-membered Ir–S–C–S chelating ring

The electronic structure and photophysical properties of two series of iridium(iii) complexes with a four-membered Ir–S–C–S chelating ring have been theoretically studied using the DFT and TDDFT method.

Theoretical insight into the photophysical properties of six heteroleptic Ir(iii) phosphorescent complexes bearing ppy-type ligands

By using density functional theory and time-dependent density functional theory, the geometrical, electronic and photophysical properties of six complexes with two ppy-type ligands and one acetylacetone anion around the Ir center have been explored. The lowest energy absorption wavelengths are located at 414 nm for 1, 434 nm for 2, 434 nm for 3, 421 nm for 4, 436 nm for 5, and 425 nm for 6, respectively. The lowest energy emissions of these complexes are localized at 617, 492, 633, 634, 491 and 491 nm, respectively, for complexes 1-6, simulated in CH2Cl2 medium at the M062X level. The calculated lowest lying absorption wavelength and the lowest energy emission wavelength for complex 3 are very close to the available experimental values. The position and number of the incorporated electron-withdrawing fluorine substituents have some effect on the electronic and photophysical properties of these studied complexes.

A remarkable phosphorescent sensor for acid–base vapours based on an AIPE-active Ir(iii) complex

A novel AIPE-active neutral mononuclear Schiff base ligand Ir(iii) complex has been synthesized for rapid and reversible phosphorescent sensing of acid–base vapours.