Circularly polarized narrowband phosphorescent organic light-emitting diodes

Abstract

Design strategies for chiral iridium(III) complexes with stable circularly polarized luminescent properties have emerged as important research topics in the field of organic photonics. Given the high rigidity, low chemical activity and multi-closed-loop structure of R-camphor, its chirality cannot be easily affected. Furthermore, the introduction of indolo[3,2,1-jk]carbazole is beneficial for the 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 to elucidate their photophysical properties, chiroptical properties, electrochemical behaviors, theoretical calculations and electroluminescence. The maximum emission peak of racemic Δ/Λ-(mpincz)₂Ir(R-camphor) in a degassed toluene solution is located at 560 nm with a full width at half maximum (FWHM) of 48 nm, which demonstrated strong circularly polarized photoluminescence (CPPL) in toluene solution with a luminescent dissymmetry factor (g_PL) of 1.15 × 10⁻³ and −1.0 × 10⁻³, respectively. Based on Δ-(mpincz)₂Ir(R-camphor) and Λ-(mpincz)₂Ir(R-camphor), efficient organic light-emitting diodes (OLEDs) were fabricated via vacuum evaporation deposition, with maximum external quantum efficiency (EQE_max) values of 14.65% and 15.58% and asymmetry coefficients (g_EL) of 1.86 × 10⁻⁴ and −2.29 × 10⁻⁴, respectively. This work may provide an effective strategy for the preparation of circularly polarized narrowband Ir(III) complexes.