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

In order to realize full colour displays of polymer light-emitting diodes (PLEDs), it is desirable to utilize light-emitting polymers that emit blue, green and red light (the three primary colours). We have succeeded in developing a new strategy to design highly efficient green light-emitting polymers based on the dopant/host concept used to design high performance organic light-emitting diodes (OLEDs). Our new strategy is to covalently attach a very small amount of a highly fluorescent green dye (dopant) to the side chain of a blue polyfluorene (host). The resulting new polymer can be considered as a molecular dispersion of a green dopant in a blue polymer host. This new strategy is distinctly different from the previous state-of-the-art strategy, in which a high content of a narrow bandgap unit is incorporated into the main chain of a conjugated polymer, in terms of photophysical properties, electrochemical properties, electron/hole injection and transport properties because of the energy transfer and charge trapping from the host to the dopant.

2. What has motivated you to conduct this work? 

Highly efficient green light-emitting polymers are still very limited. Our molecular design is based on the fact that the dopant/host strategy has been successful in tuning the light emission colour and enhancing the efficiency and stability of organic light emitting diodes (OLEDs) based on small molecules, suitable for practical applications. Hence, we apply this dopant/host concept to the design of novel green light-emitting polymers by covalently attaching the dopant to the polymer host.

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

Our results have demonstrated that electroluminescent polymers based on the dopant/host strategy, which exhibit complete molecular dispersion, are very promising for display applications. Based on this strategy, highly efficient light-emitting polymers with different emission colours (blue, green, red, even white) can be developed. By optimizing the chemical structures of the dopant unit and the host polymer, the performance of the resulting polymers can be further enhanced. It is anticipated that more research will be directed towards the understanding and device optimization of electroluminescent polymers that adopt the dopant/host concept and molecular dispersion feature.

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

Light-emitting polymers that adopt the dopant/host concept and molecular dispersion feature are distinctly different from those of the state-of-art light-emitting polymers. Therefore, the modification of the chemical structure of the dopant/host polymers with efficient energy transfer and charge trapping effects and the optimization of the device structure and fabrication procedure are desirable to achieve long lifetime and high efficiency of the resulting PLEDs.