| 초록 |
Metal nanoparticles are known to exhibit unique optical properties in the visible spectral range due to the excitation of the collective oscillations of conducting electrons known as plasmon resonances or surface plasmons, strongly affects the spectroscopy of nearby molecules. These are essentially light waves that are trapped on the surface because of their interaction with the free electrons of the conductor. These oscillations can occur at the interface between a metal and a dielectric medium. Excitation of localized surface plasmons by an electric field(light) at an incident wavelength where resonance with free electrons occurs results in strong light scattering, in the appearance of intense surface plasmon absorption bands, and an enhancement of the local electromagnetic fields. The frequency and intensity of the surface plasmons absorption bands are characteristic of the type of material, and are highly sensitive to the size, size distribution, and shape of the nanostructures, as well as to the environments which surround them. Due to the quenching of emission by surface plasmons in the light emitting device, only few attempts have so far been made for surface plasmons to be applied for organic light emitting devices. Recently, it was reported that the presence of metal particles or metal films in the light emitting device can enhance the light emission. But several problems exist for metal particles or metal films to apply for organic light emitting devices. Examples of these problems would be quenching of light and phase separations. In our presentation, we demonstrate enhanced PL intensity of organic fluorophores and effects on the OLED device performance by using Ag thin film as a metal functionalized layer on the ITO which exhibit surface plasmons in the visible spectral region. This enhancement attributed to two factors. The first factor is local enhancement of the incident electromagnetic field causing absorption. The second factor is increased radiative rates for molecules near the silver thin film. The samples used our experiment were prepared by inserting metal functionalized layer into OLED structure. We studied four different light emitting materials, namely poly(N-vinylcarbzole) (PVK), Poly[9,9-di-(2’-ethylhexyl) fluorenyl-2,7-diyl] (PFOs), poly[2-(5-cyano-5-methylhexyloxy)-1,4-phenylene] (CN-PPP) and poly [2-methoxy, 5-(2’-ethyl-hexyloxy)-1,4-phenylenevinylene] (MEH-PPV). |
