Light emitting electrochemical cells and compounds

Abstract

Charged organic thermally activated delayed fluorescence (TADF) species are described. A light-emitting electrochemical cell (LEEC) includes the charged organic thermally activated delayed fluorescence (TADF) species and sufficient counter ions to balance the charge on the charged organic thermally activated delayed fluorescence species, as emitter material. Also disclosed are OLEDSs containing the TADF species.

Description

FIELD OF THE INVENTION[0001]The present invention is directed to the provision of Light Emitting Electrochemical Cells (LEECs) and luminescent emitter compounds for use in LEECs, in particular to Thermally Activated Delayed Fluorescence (TADF) compounds for use in LEECs or other light emitting devices.BACKGROUND TO THE INVENTION[0002]Organic Light Emitting Diodes (OLEDs) have come to the fore as the state-of-the-art technology for visual displays and lighting. OLEDs are desirable as they are light weight, flexible, provide better contrast and possess large viewing angle. OLEDs are also more power efficient than traditional lighting sources and thus their wide adoption can alleviate significantly the strain on current energy demand because lighting alone constitutes about 20% of energy consumption worldwide.[0003]The “first generation” OLEDs were based on organic fluorescent emitters whose efficiency was intrinsically capped at 25% due to only being able to recruit singlet excitons. ...

AI Technical Summary

Benefits of technology

The patent text describes a new type of organic material that can be used in light-emitting electrochemical cells (LEECs). This material is a charged organic thermally activated delayed fluorescence (TADF) species that does not contain a metal. This absence of metal reduces cost and avoids potential toxicity. The TADF species has good solubility, making it suitable for solution processing, such as inkjet printing, and can also be fabricated in air and use air stable electrodes. The text also mentions that the emitter material of the LEEC can be made of a TADF species with phosphine oxide or phosphine sulphide acting as a modifier to alter the behavior of the TADF compound, resulting in changes in color and intensity of emission.

Problems solved by technology

Despite their highly desirable performance characteristics, the rarity of these metals, their high cost and their toxicity are important detracting features that inhibit large-scale, worldwide adoption of OLED technology.

However, current OLEDs, including TADF-OLEDs, still employ air sensitive electrodes requiring encapsulation, are vacuum deposited limiting the size of the device, and possess a complex multi-layer architecture that add to the cost of fabrication.

As with their use in OLEDs the use of rare heavy metal complexes in LEECs presents challenges.

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