Integration of Edge-Lit Quantum Dot Coated Lightguides in Soft Smart Surfaces

Soft smart surfaces, integrating flexible electronics and decorative materials, seamlessly combine sensors and light-emitting elements for user interaction. This allows minimalist designs for automotive interiors. To integrate uniform light-emitting elements into flexible materials, printed emissive layers like OLEDs or QLEDs can be used. These offer saturated colors but face challenges in cost, brightness, efficiency, and durability. Backlight-based technologies, such as edge-lit planar lightguides, provide a mature alternative. However, embedding such lightguides into thin, flexible stacks poses significant challenges, particularly in maintaining total internal reflection due to the need for air gaps. This work presents the design and fabrication of an edge-lit lightguide with a quantum dot (QD) color conversion layer, fully integrated into a soft, flexible polyurethane resin (PUR) layer laminated on a polyethylene terephthalate (PET) substrate containing electronic circuitry and blue LEDs. The spreading of the light within the lightguide, to obtain uniform light-emitting icons and symbols, is realized by employing diffuse reflective paint layers and optimizing the lightguide shape. Optical ray tracing simulations, based on accurately measured material properties, were used to determine the required QD loading in the 100 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu \mathrm{m}$</tex-math></inline-formula> thick QD layer to achieve the targeted color, as well as analyze the performance of the configuration in detail. The final design was validated through light output measurements from a fabricated prototype.