Design and synthesis of fast kRISC MR-TADF emitters: merge of cycloparaphenylene materials and B,O doped MR-TADF emitters (CPP-MR-TADF)

Organic light-emitting diodes (OLEDs) are nowadays omnipresent in the form of display screens in mobile phones and smartwatches. Although already commercialized, this technology still possesses shortcomings. For instance, OLEDs use scarce noble metals like iridium as emitters for the red and green pixels of the display, making the technology in its present form not sustainable. Introduced for the first time in 2015, multiresonant thermally activated delayed fluorescence (MR-TADF) emitters, which are organic compounds, allow to produce OLEDs at comparable efficiency and color point to phosphorescent OLEDs, but are sustainable. However, OLEDs with MR-TADF materials presently suffer from a too high efficiency roll-off related to the slow reverse intersystem crossing rate (kRISC), strong intermolecular interactions/aggregation that cause emission quenching, and poor charge transport properties. This project proposes the development of a new class of luminescent materials that brings together facets of MR-TADF emitters and cycloparaphenylene (CPP) materials. CPPs are pure hydrocarbon organic semiconductors that possess a cylindrical geometry, which strongly limits intermolecular interactions in the solid state. This fundamental proposal explores the theoretical modelling, synthesis, and optoelectronic characterization of a family of hybrid CPP-MR-TADF materials as potential emitters for OLEDs. The proposed multidisciplinary strategy aims to provide a sought-after solution to increasing kRISC in MR-TADF materials while also addressing issues of charge transport in the emissive layer and the propensity for these molecules to undesirably aggregate.