A Composite from Poly(m‐phenylenevinylene‐co‐2,5‐dioctoxy‐p‐phenylenevinylene) and Carbon Nanotubes: A Novel Material for Molecular Optoelectronics

摘要: As research progresses towards smaller and more efficient devices, the need to develop alternative molecular scale electronic materials becomes apparent. Integrated component fabrication from organics has been recognized theoretically as ultimate goal. In order gain a comprehensive insight into these materials, extensive carried out on conjugated carbon systems over last few decades optimize their optical electrical properties. For example, doping polyacetylene with I2 shown result in large increase conductivity compared pristine material. However, polymers tends retard properties regards luminescence by reducing bandgaps introducing trapping sites such solitons, polarons, or bipolarons. The simple lesson years is that if are be considered for luminescence, should not despite desire improve charge transport We report here first physical adopingo, use traditional term, using small concentrations of multiwalled nanotubes luminescent polymer, poly(m-phenylenevinylene-co-2,5-dioctoxyp-phenylenevinylene) (PmPV), polymer/nanotube composite. This can polymer up eight orders magnitude. appear act nanometric heat sinks, preventing buildup thermal effects, caused either optically (photobleaching) electrically, which degrade systems. also electroluminescence was achieved an organic light-emitting diode (LED) composite emissive layer device. Since initial work systems, attempts have made find area where and/or fullerenes could used active semiconductor components. Although many new interesting synthesized this end, very found practical application. One exception polyphenylenevinylene (PPV), reported Burroughes et al. being Schottky diode. encouraged scientists study wide variety including derivatives efficiency light emission devices. Polymers LEDs must possess number important qualities. A high quantum yield photoluminescence necessary material remain undoped, dopants sites, quenching radiative decay excitons. It essential therefore reasonably conductive while maintaining its Most undoped low so require aturn-ono fields generate sufficient carriers produce excitons, radiatively. is, terms, inefficient generally induce consequently causing device breakdown. There other problems addressed, but elimination basic ones substantially efficiencies soon lead applications polymers. our studies PmPV, whose structure variation common PPV. case substitution pattern leads dihedral angles chain and, according mechanics energy minimization calculations, coil, forming helical structure. calculated diameter helix vacuum ca. 20 Š, whilst pitch 6 Š. Multiwalled were produced arc discharge method, resulting nm average lengths between 500 1.5 mm. nanotube powder PPV mixed together toluene sonicated briefly. probable coiled conformation allows it surround layers nanotubes, permitting sufficiently close intermolecular proximity p±p interaction occur. color change dramatic bright yellow composite, at concentrations, possesses deep green color. Photoluminescence Ar laser pump wavelength 457 nm. Electrical measured twopoint probe sandwich geometry Pt electrodes. LED fabricated casting onto indium tin oxide (ITO) then sputtering aluminum electrode top. helicity, surprising able wrap itself around keep them suspended solution indefinitely. actual texture observed Figure 1,