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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - LEO (Low-cost / energy Efficient Oleds for lighting)

Teaser

Summary

The general objective of the LEO project is to develop the technologies enabling the manufacturing of large area flexible top emission OLEDs on metal foils. For that purpose, the LEO project activities have been addressing the development of various technological building blocks including (i) low carbon steel foils adapted to OLED technologies, (ii) more performing anode material as well as novel noble metal-free OLED emitters, (iii) advanced solutions to enhance both light extraction and device durability and (iv) hybrid technology combining dry and wet OLED stack deposition processes.

Work performed

After 3 years of development, the project achieved significant progresses towards the industrialization of conformable OLEDs. With the recent production in an industrial environment of large conformable lighting metal foils (LAMP OLED) and their integration into a commercial luminaire a first decisive demonstration step has been taken. It demonstrates the effective capability of low carbon steel foils to meet the OLED market requirements once they are functionalized with the right insulating/smoothing polymer and screen printing technique in a very clean industrial environment (Osram-Oled). Compared to competing conformable OLEDs involving plastics sheets, metal foils are mechanically much more robust, constitute a natural barrier against moisture and facilitates heat dissipation.

The second remarkable output of LEO project deals with the processing in solution of noble metal-free OLED emitter materials to reduce the environmental footprint of OLED technology (Hybrid OLED demonstrator). A smart adaptation of the novel Cynora TADF materials to inkjet printing and their integration into a dry-wet hybrid process chain was conducted within LEO and enabled the collective manufacturing of R, G and B OLED stripes that exhibit noticeable characteristics with a pronounced green and blue colour saturation and efficiencies up to 20Cd/A. The devices were produced in a laboratory platform, they demonstrate however dimensions (25 cm2) consistent with future lighting market needs.

In the same manner, a conformable hard coat was developed with success that better protects mechanically the OLEDs while preserving their emission characteristics, lifetime and a certain conformability. This novel encapsulation technology uses a sol-gel formulation specifically developed by CEA in collaboration with a French company, making this product close to commercialization. Last but not least, advanced top-electrodes based on smarter optical stack designs were developed and tested. They show well enhanced light emission (up to +60%) and better colour saturation that should benefit to ambient lighting but also display applications.

Final results

Beyond these technical achievements, the LEO partners assessed the cost efficiency of the metal foil-based OLED technology. Until now, the cost reduction induced by the replacement of glass substrate by steel foils turns out to be more limited than expected but offers new features (flexibility, better heat dissipation). The impact of substrate cost depends actually on the ability to massively produce high quality LCS substrates, which has not been demonstrated yet. In return, the replacement of conventional encapsulation solution (cover glass) by the novel hard coat technology developed by CEA clearly shows the highest cost saving potential. In the same manner, the choice of TADF polymer coupled to an inkjet technology could induce a significant material cost saving. Overall the OLED cost can be reduced by ~20% while achieving new features (flexibility).
The LEO partners are already busy exploiting the projectâ€™s results. OSRAM, for instance, is focusing on process integration for both hybrid systems and metal-based OLEDs in automotive applications and special applications in general illumination. ArcelorMittal keeps on developing new materials and coatings based on R2R process technologies, as implemented in LEO, to produce advanced steel foils for printed electronics applications. Cynora is providing state-of- the-art TADF materials to worldwide leading panel makers, and CEA notably aims to transfer its encapsulation knowledge to both OLED and photovoltaic device manufacturers. Unexpected applications are also emerging beyond lighting. These include conformable OLED panels for aeronautics (patent pending), as well as display applications requiring higher image contrast than the conventional glass cover approach.