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ORGANIC EMITTERS
Light-emitting fabrics
Light-emitting bres that suit integration with textiles are prepared by dip-coating a steel wire with an electroluminescent material and then cleverly wrapping the structure with a carbon nanotube sheet that functions as a transparent electrode.
Enrique Ort and Henk J. Bolink
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Organic light-emitting devices are very appealing for a wide variety of applications, ranging from displays
to lighting, as they oer a bright source of light with a wide colour gamut and can be applied to rigid, curved and even exible substrates. Their high versatility is in part due to the very thin active organic layers used, which are less than a micrometre thick yet can cover large areas (hundreds of square centimetres).
The technological and economicimpact of organic light emitters is already considerable but would be further increased if a convenient means could be found to integrate such emitters into fabrics, thus enabling wearable displays and lighting. This, however, is not a trivial task as fabrics themselves are not directly suitable for use as device substrates. However, if one could create a light-emitting device in a bre geometry that could be woven or knitted into fabrics it would open up all kinds of opportunities. And this is exactly what Zhang et al.1 report in this this issue of Nature Photonics.
One of the simplest types of organic light-emitting devices consists of justone electroluminescent layer sandwiched between two electrodes (one of whichis semi-transparent to allow the light to escape from the device). Of particular interest are light-emitting devices in which salts have been added to the single active layerreferred to as light-emitting electrochemical cells, or LECs, by their inventors twenty years ago2.
In LECs, light emission is largely independent of the type of electrodes employed due to the presence of ions inthe active layer. When the device is turned on, that is, when a voltage is applied, the salts ions migrate to the electrode interface, which leads to a strong reduction of the injection barrier for electrons and holes. Following charge injection, light emission starts and highly conductive regions are formed that render these devices less sensitive to the surface roughness of the electrodes3. Their insensitivity to the
electrode work function and roughness makes LECs an...