| Because of the fast response, wide viewing angle, self-luminous and other advantages, organic light-emitting diodes (OLEDs) are widely concerned. In particular, phosphorescent materials can also use triplet to increase the internal quantum efficiency to 100%, which can improve luminous efficiency. In general, the phosphorescent material used the host-guest doping structure, but the development of blue phosphorescent are lagging behind the red and green phosphorescent devices due to the lack of appropriate host material.In this paper, we synthesis double chain Si-O-Si as the backbone of the polymer skeleton, and carbazole and triphenyl phosphine as a pendant light-emitting group. In order to ensure the ladder-shape-structure of the product, the polymerization method is as follows: first, the monomer is self-assembled, then fixed by freeze-drying on the inner surface of the bottle to carry out in situ condensation polymerization, and finally polymerized in the solution. We have successfully synthesized bipolar host material (LPCzSiPO) and another two polymer (LPDCzSi, LPDPOSi) as comparison. Due to the introduction of siloxanes, they have good thermal stability, where the bipolar host material has Td = 451 ?, Tg = 178 ?,the siloxanes also blocked the conjugation between the pendant groups and improved the triplet energy (ET=2.93, 3.00, 3.01), higher than FIrpic. The HOMO and LUMO values of the three polymers were tested by voltammetry, while the bipolar polymer not only had a higher HOMO value (-5.32) to match the work of ITO/PEDOT:PSS, and because of the introduction of triphenyl- phosphine, the LUMO value (-1.93) is lower than the single hole transport matial, which is favorable for electron injection.According to the DFT, the distribution of HOMO and LUMO in the bipolar host is better than that of the single hole and the single electron host material, which is completely distributed in different groups, reduce group interaction, and beneficial to electron and hole transport respectly. |
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