OLEDs Become Brighter and More Durable

Organic light-emitting diodes become brighter and more durable. Layers made as ultrastable glasses improve device performance. (Source: TU Dresden)

Organic light-emitting diodes truly have matured enough to allow for first commer­cial products in the form of small and large displays. In order to compete in further markets and even open new possi­bilities as automotive lighting, head-mounted-displays, micro displays, etc., OLEDs need to see further improve­ments in device lifetime while operating at their best possible effi­ciency. Currently, intrinsic perfor­mance progress is solely driven by material develop­ment.

Now, researchers from the Univer­sitat Autònoma de Barcelona and Tech­nische Univer­sität Dresden have demon­strated the possi­bility of using ultra­stable film formation to improve the perfor­mance of state-of-the-art OLEDs. The researchers show in a detailed study that signi­ficant increases of effi­ciency and opera­tional stabi­lity – > 15% for both para­meters and all cases, signi­ficantly higher for indi­vidual samples – are achieved for four different phos­phorescent emitters. To achieve these results, the emission layers of the respec­tive OLEDs were grown as ultra­stable glasses – a growth condition that allows for thermo­dynamically most stable amorphous solids.

This finding is signi­ficant, because it is an optimi­zation which involves neither a change of materials used nor changes to the device archi­tecture. Both are the typical starting points for improve­ments in the field of OLEDs. This concept can be univer­sally explored in every given specific OLED stack, which will be equally appre­ciated by leading industry. This in parti­cular includes thermally acti­vated delayed fluores­cence (TADF) OLEDs, which are seeing tremen­dous research and develop­ment interest at the moment.

Further­more, the improve­ments, that can be tracked back to dif­ferences in the exciton dynamics on the nano­scale, suggest that other funda­mental proper­ties of organic semi­conductors – transport, charge sepa­ration, energy transfer – can also be equally affected. Currently, this concept is being explored together with Cynora GmbH, a Mostophos partner and a world-leading company in develop­ment of TADF emitters. (Source: TU Dresden)

Reference: J. Ràfols-Ribé et al.: High-performance organic light-emitting diodes comprising ultrastable glass layer, Sci. Adv. 4, eaar8332 (2018); DOI: 10.1126/sciadv.aar8332

Link: Dresden Integrated Center for Applied Physics and Photonic Materials, Technische Universität Dresden, Dresden, Germany

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