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

In this context, a series of platinum complexes containing a triphenylene unit, namely Pt5single bondPt8, 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.