Deep blue electroluminescent phenylene-based polymers

We synthesize a series of soluble phenylene-based electroluminescent (EL) polymers with deep blue emission by incorporations of dialkoxy groups (DRO-PPP) and alkoxy-phenyl group (EHB-PPP) on side chains as well as carbazole unit on main chain (EHB-PPP-Cz) using the Yamamoto coupling approach. The latter two modifications (EHB-PPP and EHB-PPP-Cz) lead to blue-shifts in absorption and emission maxima relative to DRO-PPP. In addition, the incorporation of carbazole as co-repeat-unit (EHB-PPP-Cz) leads to a raise of ionization potential (IP) to the level very close to that of the anode, PEDOT:PSS, to facilitate the hole injection. The maximum efficiency of the ITO/PEDOT:PSS/EHB-PPP-Cz/TPBI/CsF/Ca/Al device is 1.12 cd/A with a stable deep blue EL with CIE (0.16, 0.05).