Chiral Platinum‐Based Metallomesogens with Highly Efficient Circularly Polarized Electroluminescence in Solution‐Processed Organic Light‐Emitting Diodes

Abstract Circularly polarized luminescence (CPL) is of interest due to its wide potential application in semiconductors. To balance the emission efficiency and luminescence dissymmetry factor ( g PL ) of a CPL emitter, in this context, two chiral, phosphorescent and liquid‐crystalline cyclometalated platinum complexes, abbreviated R ‐Pt and S ‐Pt, are prepared. The complexes, which show an intense green emission at 504 nm both in solution and in the solid state, contain a simple, ortho ‐metalated 2‐phenylpyridine unit functionalized with a chiral 2‐octanol chain, with liquid crystallinity being induced by modifying the β‐diketonato ligand with mesogenic groups. Interestingly, both the chiral smectic (SmA*) and nematic (N*) phases are found by a combination of polarized optical microscopy, differential scanning calorimetry, and small‐angle X‐ray scattering. By annealing, distinct CPL emission is achieved in the solid state with a g PL around 0.02. Employing the chiral platinum complexes as the dopant, solution‐processable organic light‐emitting diodes present an external quantum efficiency of 11.3% and strong, circularly polarized electroluminescence with an extremely high luminescence dissymmetry value ( g EL ) of 0.06 after annealing at 100 °C. This work opens an avenue for designing CPL‐active emitters with high emission efficiency and high dissymmetry factor.