Development of highly efficient solution-processable blue organic light-emitting diodes based on liquid-crystalline thermally activated delayed fluorescent emitter materials

Recent years have seen tremendous advances in the area of vacuum-deposited organic light-emitting diodes (OLEDs) and these are now commercialized as displays in small portable devices, flat-panel full-colour televisions, and solid-state lighting sources for the automotive industry.

The state-of-the-art emitters in these devices consist of a combination of fluorescent and phosphorescent materials, each of which has weaknesses in terms of performance and sustainability. Thermally activated delayed fluorescent (TADF) emitters offer the potential to overcome these weaknesses.

Vacuum-deposition fabrication processes are, however, both costly and materials-wasteful and it is also difficult and expensive to fabricate large-area pixels given the size of the evaporator. Solution-processed OLEDs addresses these detracting features of the fabrication process.

The state-of-the-art solution-processed OLEDs, and in particular blue OLEDs typically show poor device performance both in terms of stability and external quantum efficiency (EQE) that is significantly worse than vacuum-deposited devices. This proposal addresses these specific issues using an innovative approach.

We will develop solution-processable blue TADF emitters based on discotic liquid crystalline (DLC) molecules, which we contend will provide horizontal alignment in solution-processed films, something not possible at present, in order to improve the light-outcoupling efficiency and hence the EQE.