Abstract
Organic optoelectronic devices based on conjugated polymers attract a lot of interests in the past decade due to the possibilities of low cost large-area solution process on flexible surfaces.Such unique properties are highly desirable for the development of sensitive skin for a moving machine like robot or car. The conventional proximity sensor based on inorganic near infrared light-emitting diodes and photo-detectors can not be integrated by monolithic fabrication as an array on flexible substrate which is essential for robots and other machine surfaces. Contrarily it is rather easy to fabricate polymer light-emitting diodes (PLED) and polymer photo-detectors on plastic substrates with a high pixel density. A proximity sensor which combines a polymer light-emitting diode and a polymer photodiode is presented. The operation wavelength is in the near infrared 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 to a visible-light 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 methyl ester. When the PLED is biased at 9 V the reflected light is strong enough and the detection distance is up to 19 cm for objects with various colors and roughness under ambient indoor lighting.