Thermally cross-linkable host materials for enabling solution-processed multilayer stacks in organic light-emitting devices

• A novel cross-linkable host material, DV-CBP, for use in solution-processed OLEDs.
• DV-CBP was thermally cross-linked by curing at approx. 180 °C without initiators.
• The PLQEs of the emissive layer were maintained above 75% throughout the reaction.
• An additional layer was deposited on top of the cross-linked layer by spin-coating.
• The multilayer device showed superior performance to Ca-based single layer devices.

A thermally cross-linkable host material, i.e., two vinylbenzyl ether groups containing a carbazole derivative (DV-CBP), was developed for solution-processed multilayer organic light-emitting devices (OLEDs). DV-CBP was thermally cross-linked at styrene end-groups through curing at approximately 180 °C in the absence of a polymerization initiator. This cross-linking reaction rendered the emissive layer insoluble and enabled the subsequent solution deposition of an upper electron-transporting layer. Furthermore, photoluminescence quantum efficiencies of the emissive layer were maintained at greater than 75% throughout the cross-linking reaction. A solution-processed small-molecule electron-transporting layer on top of the cross-linked emissive layer led to lower driving voltages and higher efficiencies in the OLEDs compared to those of a device with a vacuum-deposited Ca electrode on the emissive layer.

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