Making highly efficient white light-emitting diodes
White organic light-emitting diodes offer a power efficiency, lifetime, and brightness that together constitute a significant advance toward viable devices for lighting.
Light-emitting diodes (LEDs) are used in both displays and illumination applications because they are small, robust, and potentially very efficient. Organic light-emitting diodes (OLEDs) continue to gain attention from the scientific and industrial community. In contrast to their inorganic counterpart, OLEDs are flat and diffuse area light sources with the device thickness being in the range of 1–2mm. Thus far, OLED development has been triggered mainly by applications in the display segment, starting with applications for MP3 music players, mobile phones, and other portable devices. Recently, Sony brought to market the first OLED TV, which indicates that a more general penetration of the display market is close at hand.
OLEDs have not yet entered the lighting market, but that will probably change soon. Already most of the big players in the field are preparing for OLEDs to become ‘the next big thing.’ However, several critical problems need to be solved before widespread use for lighting becomes feasible. Specifically, the lifetimes, power efficiencies, reliability, and cost-effectiveness of white OLEDs must be able to compete with existing lighting technologies.
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