Polycarbazole-based networks made by photo-crosslinking for hole transporting layers of OLED devices

Cross-linkable polycarbazole copolymers have been synthesized starting from 3,6-diiodo-9-(2-ethylhexyl)carbazole and 3,6-diodo-9-[6-(3-ethyloxetan-3-ylmethoxy)hexyl]carbazole monomers in a Ni(0)-catalyzed Yamamoto-type aryl–aryl coupling. The synthesized materials were characterized by various techniques including differential scanning calorimetry, thermogravimetry and cyclic voltammetry. Insoluble layers of the copolymers have been obtained by photo-crosslinking thin films of the materials. Organic light emitting diodes using the crosslinked polycarbazole networks as hole transporting layer demonstrated a turn-on voltage of ca. 4 V, a maximum brightness of 15,000 cd/m2, and maximum OLED efficiency of 8.5 cd/A.

Graphical abstractLuminous efficiency of the devices: ITO/PEDOT or crosslinked PKOx/GEP/(Ca/Al).Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Cross-linkable polycarbazole copolymers have been synthesized. ► Insoluble layers from the copolymers were obtained by photo-cross-linking. ► OLEDs using the networks demonstrated maximum brightness exceeding 15000 cd/m2. Maximum OLED efficiency was 8.5 cd/A.