Multi-resonance TADF materials for highly efficient and stable OLEDs

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Advanced materials underpin most modern technologies including electronics, communications, displays, lighting and solar cells. Light-emitting materials are of particular interest because they can be used for lighting, information display and lasers. The purpose of this project is to develop new light-emitting materials with high efficiency, purity of colour and stability. The materials will emit light when a voltage is applied to them in devices called organic light-emitting diodes (OLEDs). OLEDs are used to make television, mobile phone and smartwatch screens with excellent contrast and vivid colours, that can be viewed clearly from a wide array of angles as well as straight on. OLEDs are also an important emerging lighting technology. Efficient OLED materials will reduce energy consumption and so contribute to reaching the UK's ambitious target of net-zero carbon emissions by 2050.Commercial OLED materials can give efficient red and green emission but contain very rare and expensive metals such as iridium; the blue emitter is much less efficient as it does not contain the metal. A newer generation of OLED materials achieve high efficiency by a process called thermally activated delayed fluorescence (TADF), but usually have broad emission spectra, leading to colours that are not pure red, green or blue, and so do not satisfy the stringent industry requirement for these colours. We will explore an emerging class of TADF materials that overcomes these limitations by using so-called "multi-resonant" TADF structures that are much more rigid. This rigidity leads to narrow emission spectra and hence purer colours, and in addition improves the stability of the materials, which is key to improving the stability of the corresponding OLEDs. Capitalizing on our recent published work in this area, we will combine insights from chemistry and physics to develop new classes of MR-TADF emitters that give efficient red, green and deep blue emission. We will further enhance the efficiency of OLEDs by making some of the first examples of these materials that are aligned in a way to enable more light to escape from the devices.