Conjugated polymers have attracted considerable attention as a new class of electronic material, since the study of these systems has generated entirely new scientific concepts as well as potential for new technology. Conjugated polymers are organic semiconductors and as such important materials for applications in electronic and photonic devices. Prime examples are polymeric light-emitting diodes, plastic lasers, and polymer based photovoltaic cells, but at least in principle, conjugated polymers should be able to pertain all of the functions an inorganic semiconductor displays, FETs, and may lead in the future to "molecular electronics". The primary advantage of organic polymers over their inorganic counterparts is their ease of processing by dip coating, spin casting, printing, or use of doctor blade techniques. However, conjugated polymers are likewise important as sensory materials for water, organic vapors, and explosives either by fluorescence quenching or in artificial nose devices, which change their conductivity upon exposure to a suitable analyte.