Circularly polarized narrowband phosphorescent organic light-emitting diodes

Abstract

Design strategies for chiral iridium (III) complexes with stable circularly polarized luminescent properties have been emerged as important ongoing research tasks in the field of organic photonics. Given the high rigidity, low chemical activity and multi-closed-loop structure, the chirality of R-camphor can not be easily affected. And the introducing of indolo[3,2,1-jk] carbazole is beneficial for narrow emission spectrum. Thus, two yellow-emission chiral iridium(III) isomers, Δ-(mpincz)2Ir(R-camphor) and Λ-(mpincz)2Ir(R-camphor), were designed and systematically investigated towards photophysical properties, chiroptical properties, electrochemistry behaviors, theoretical calculations and electroluminescence. The maximum emission peak of the racemic Δ/Λ-(mpincz)2Ir(R-camphor) in degassed toluene solution is located at 560 nm with the full width at half maximum (FWHM) of 48 nm，which also demonstrated strong circularly polarized photoluminescence (CPPL) in toluene solution with the luminescent dissymmetry factor (gPL) of 1.15 × 10-3 and -1.0 × 10-3, respectively. Based on Δ-(mpincz)2Ir(R-camphor) and Λ-(mpincz)2Ir(R-camphor), the efficient organic light-emitting diodes (OLEDs) were fabricated by vacuum evaporation deposition, with the maximum external quantum efficiency (EQEmax) of 14.65% and 15.58%, respectively and the asymmetry coefficients (gEL) are 1.86 × 10-4 and -2.29 × 10-4, respectively. This work may provide the effective strategy for the preparation of circularly polarized narrowband Ir(III) complexes.