Influence of integrated alkyl-chain length on the mesogenic and photophysical properties of platinum-based metallomesogens and their application for polarized white OLEDs

• A series of platinum complexes, Pt5P8, containing triphenylene unit were prepared and characterized.
• Complex Pt6 exhibits a column phase evidenced by DSC, POM and XRD.
• All of platinum complexes show intense emission both in solution and solid state.
• Polarized white OLED with polarized ratio of 1.4 was achieved in Pt6-based device.

In this context, a series of platinum complexes containing a triphenylene unit, namely Pt5Pt8, was prepared and characterized. Platinum complex Pt6 shows a clearly column liquid crystalline property, confirmed by differential scanning calorimetry, polarized optical microscopy and X-ray diffraction. These platinum complexes only display monomolecular emission both in solution and in neat film, an effect attributed to the presence of carbazole as a bulky group disfavoring aggregation of the complexes. Hole mobilities in the range of 10−5–10−6 cm2 V−1 s−1 were obtained for the annealed platinum complexes films. It was found that the method to align the emissive layer has a crucial role on the performance of the devices. The first example of polarized phosphorescent white organic light-emitting diode (OLED) with polarized ratio of 1.4 was achieved in Pt6-based device. This research opens up a new aspect of phosphorescent metallomesogens application for polarized white light emission.

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