Light Emitting Diode of Fully Conjugated Heterocyclic Aromatic Rigid-rod Polymer Doped with Multi-wall Carbon Nanotube

摘要

Poly-p-phenylenebenzobisoxazole (PBO) and carbon nanotube (CNT) contain fully conjugated rodlike backbone entailing excellent mechanical properties, thermo-oxidative and solvent resistance. Rigid-rod PBO is commonly processed by dissolved in methanesulfonic acid or Lewis acid. A CNT of multi-wall carbon nanotube (MWNT) was dissolved in a Lewis acid solution of PBO for dispersion of nanotube, and then spun for thin film. MWNT concentration in the films was from zero up to 5 wt. %. Compared to that of pure PBO film, all PBO/ MWNT composite films retained same but enhanced UV-Vis absorption peaks showing that MWNT and PBO do not have overlapping electron orbitals affecting their energy gaps. The composite films were excited at 325 nm using a He-Cd laser for photoluminescence (PL) response. All PL spectra had maximum wavelength peak at 540 nm indicative of yellow-green light emission. In the case of light emitting diodes, MWNT doped PBO would decrease threshold voltage for about 2 V and increase device emission current up two orders of magnitude than those without MWNT. This required a larger bias voltage leading to a shorter device lifetime.