1. Could you explain the significance of your article to the non-specialist? 

One of the great advantages of OLEDs fabricated by thermal deposition, over PLEDs fabricated by solution processing is that thermal deposition allows multilayer devices to be built, where electrons and holes are confined in the narrow recombination zone which results in good carrier balance and thereby high efficiency. A challenge to the fabrication of multilayer devices via solution processing in PLEDs is that the application of subsequent layers does not result in the erosion of the layers that have been applied in the previous steps. Although the development of crosslinkable hole transportable materials can solve this problem, additional high temperature crosslinking steps makes device fabrication time-consuming. Therefore, we propose an easy and cost-effective strategy using hole transport materials processable in solvents in which emitting polymers are not soluble.

2. What has motivated you to conduct this work? 

The utilization of triphenylamine derivatives as hole-transport materials has proved very successful in OLEDs. We previously successfully developed a new type of water/alcohol soluble polyelectrolyte as an electron-injection and hole-blocking materials for bilayer cathode which was used to build multiplayer devices by solution processing without interface-mixing with the emitting layer underneath. A similar strategy was applied to hole transporting/electron blocking materials in this report.

3. Where do you see this work developing in the future? 

Preliminary results reported in this paper suggest that the strategy is promising. We are currently working on further improvement of device efficiency by synthesising varieties of new water/alcohol soluble hole transporting layer/electron blocking layer materials via structure optimization.

4. Are there any particular challenges facing future research in this area? 

Yes. A great challenge in the PLED field is to develop water/alcohol soluble hole transport layer/electron transport layer HTL/ETL materials which combine good device efficiency, long operating life, low operating voltage and ease in processing. Only materials which fulfill all these requirements will find a place in flat-panel display technology.