Screen display technology is taking a significant step forward as researchers from Sony and the Max Planck Institute demonstrate the possibility of bendable optically assessed organic light emitting displays for the first time, based on red or IR-A light upconversion.
The paper, Annihilation Assisted Upconversion: All-Organic, Flexible and Transparent Multicolour Display, makes feasible the design of computers that can be folded up and put in your pocket, the mass-production of moving image posters for display advertising, televisions which can be bended to view, or even newspaper display technology, which allows readers to upload daily news to an easy-to-carry display contraption.
Organic, upconversion multicolour displays have significant advantages when compared to the traditional technology used for projection displays and televisions. For example: the displays have an ultra-low excitation intensity (red or IR); the display is emissive with no speckles; coherent or non-coherent excitation is allowed; the displays have a high efficiency – at around six per cent; fast response times – circa one µs up to 500µs on request (LCDs have millisecond response times); an almost unlimited viewing angle – up to the total internal reflection angle; the emitted colours can be tailored even when using the same excitation source; multilayer displays and are only size limited only by the size of the substrates.
With LCD-based projection displays, the liquid crystal acts as a filter for the light being shone through so when coherent excitation is used (e.g. laser diodes) the problems with speckles are serious. For this organic emissive UC displays, the organic molecules themselves emit non-coherent light in 4p (all directions) to produce an image.
Sony announced the development of flexible OLED display screens in 2006, but glitches such as size and resolution limitations, and the difficulty of structuring the organic compounds so as not to be distorted when bent, have stopped designs coming to market. This new technology for optically excited organic emissive displays has not got this problem and gives further opportunities for new applications.
