Direct Printing of Light-Emitting Devices on Textile Substrates

Smart textiles are a rapidly expanding field in the world of textiles, announcing a new and intriguing era. Different functionalities can be added to the textile to make the textile smart and intelligent. One of these functionalities is the addition of light-emitting layers or devices that can be incorporated into the textiles. These light-emitting textiles find a broad application in the field of interior and exterior design and wearable applications. Depending on the application, two light-emitting devices, the alternating current powder electroluminescent (ACPEL) device and the organic light emitting diode (OLED), both consisting out of a stack of thin layers, can be directly printed on top of the textile substrates. With its relatively high AC voltage of 50–200 V, the ACPEL device is more suited for interior and exterior applications while the OLED with a low DC voltage of 3–5 V is a perfect candidate for wearable applications. To maintain typical textile properties such as flexibility, breathability and drapability, different smart designs of the ACPEL devices are suggested, screen printed and analysed. More challenging is to apply the OLEDs on textile substrates. The very thin nanometre range layers make a planarizing layer to smoothen the textile surface indispensable. Different techniques such as spin coating, ultrasonic spray coating, inkjet printing and thermal evaporation are used to apply the complete OLED stack.