NOVELTY - Monomer, oligomer or polymer comprising fused ring moiety (I) is new.    USE - The monomer, oligomer or polymer is useful: in an electronic device, which is organic field effect transistors, thin film transistors, integrated circuits, logic circuits, capacitors, radio frequency identification tags, devices or components, organic LED, organic light emitting transistors, flat panel displays, backlights of displays, organic photovoltaic devices, organic solar cells, photodiodes, laser diodes, photoconductors, organic photodetectors, electrophotographic devices, electrophotographic recording devices, organic memory devices, sensor devices, charge injection layers, charge transport layers or interlayers in polymer LED, Schottky diodes, planarizing layers, antistatic films, polymer electrolyte membranes, conducting substrates, conducting patterns, electrode materials in batteries, alignment layers, biosensors, biochips, security markings, security devices and components, devices for detecting and discriminating DNA sequences or organic thin film transistor, organic photovoltaic cell or organic photodiode; and as charge transport, semiconducting, electrically conducting, photoconducting or light emitting material in optical, electrooptical, electronic, electroluminescent or photoluminescent components or devices (all claimed).    ADVANTAGE - The monomer, oligomer or polymer provides high performance organic semiconductors for organic thin film transistors, organic photovoltaics, sensors or other electronic devices.    DETAILED DESCRIPTION - Monomer, oligomer or polymer comprising fused ring moiety of formula (I) is new.    X = O, S or NR;    R = H or 1-60C hydrocarbyl (optionally substituted) e.g. alkyl, alkenyl, alkynyl or aryl (all optionally substituted) or any other suitable group; and    M = conjugated moiety.    INDEPENDENT CLAIMS are also included for:    (1) a mixture or a blend comprising the monomer, oligomer or polymer and at least one compound or polymer having semiconducting, charge transport, hole transport, electron transport, hole blocking, electron blocking, electrically conducting, photoconducting or light emitting properties; and    (2) a formulation comprising the monomer, oligomer or polymer and an organic solvent.