QL-Tex: Quantum dot based electroLuminescent Textiles

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Electroluminescent (EL) devices, well-known as robust and thin display components, get increasing attention in the field of ambient lighting. Over the last years there have been efforts to implement them on fiber-based substrates to profit from the haptics and flexibility of textiles. An exciting vision of textile displays based on enmeshed light-emitting filaments drives the research activities. Unfortunately, large-area EL light-emitting devices are yet limited to few colors and overall low light intensity. More research, e.g., on new composite materials and device architectures is required to increase their performance. Our idea is to explore the application of colloidal quantum dots (QDs) in light emitters, especially in AC-driven luminescent textiles. QDs can provide a controlled expansion of the colour gamut and in addition increase the overall performance of the light-emitters, as already known from the research on LEDs, OLEDs, QLEDs and LECs. Furthermore, it was already shown, that a successful AC excitation of QDs in EL devices is principally possible. However, large-area EL light-emitting devices on flexible and/or fiber-based (textile) substrates based on QDs have not been demonstrated yet. This project will explore whether the application of colloidal QDs as an active luminescent material in EL devices can increase their performance and expand the color range, so that white luminescent textiles can be realized. Thereby in a first step blue and/or green EL emission from the established materials shall be accomplished by red-luminescent QDs to obtain a white light emission color. The controlled variation of the mixing ratios of pigments and QDs shall result in a balanced white emission with high color rendering values (CRI>80) and a controllable color temperature. For this purpose, the QDs shall be either incorporated into the dielectric layer or applied directly. In addition to the technological challenges, the excitation mechanism of the quantum dots within EL devices shall be investigated in the second step. Our hypothesis is that the use of QDs in combination with high-k dielectrics can lead to a significant reduction in the operating voltages of the EL textiles and increase of their intensity. The technological challenges of this project can only be overcome with the help of the inert gas glovebox system: all fabrication steps take place inside. The optimal device design shall be investigated, including the adjustment of process parameters during sputtering of the dielectrics and solution-based deposition of the QDs on textile substrates and filaments under controlled atmosphere. The encapsulation of the devices by parylene, which can also serve as a dielectric itself, takes place inside the glovebox system as well. Finally, the electro-optical properties of the textile lighting devices will be studied and evaluated, followed by adjustments of the material system, device architecture and fabrication processes.