Abstract
Most commercial proximity sensors are made of inorganic materials with complicated fabrication process and the processing is not compatible with flexible substrates. It will also costly when large-area applications are required such as the skin of robots. On the contrary, it is easy for organic materials to be applied in large-area and flexible substrate due to their mechanic property. The organic materials have potential for easy fabrication process and low cost. However the emission and absorption range of organic materials are usually in the visible range. In the visible range the sensing distance is very short (~1cm). For proximity sensor the infrared light is commonly used due to longer sensing distance. It is, however, difficult for organic materials to emit or absorb infrared light. Our invention as reported in this thesis is to make an infrared organic proximity sensor through a color-conversion film. The advantages of our organic proximity sensor include both long sensing distance and large-area as well as flexible application. A conjugated polymer optical proximity sensor which combines a polymer light-emitting diode and a polymer photodiode is demonstrated. The operation wavelength is in the near infrared spectrum from 700 nm to 850 nm. The infrared emission is obtained by adding a color conversion film of polyvinylpyrrolidone polymer matrix blended with infrared dye 1,1-diethyl-2,2-dicarbocyanine iodide to a red polymer lightemitting diode. The photodetector relies on the direct charge-transfer exciton generation in a donor-acceptor polymer blend of poly(3-hexylthiophene) and (6,6)-phenyl-C61-butyric acid methylester. The detection distance is up to 19 cm for objects with various colors and roughness under ambient indoor lighting.