Emission from organic light-emitting diodes via surface-plasmon cross-coupling.

摘要

This thesis discusses the use of surface-plasmon cross-coupling to enable emission from an organic light-emitting diode through an essentially opaque metal cathode. Experiments involving both photoluminescent and electroluminescent structures were performed to evaluate the efficacy of this mechanism. Emission from photoluminescent samples through a corrugated, opaque silver film was measured to be over an order of magnitude stronger than that from a flat sample with no metal overlayer. Emission through a silver cathode was also observed in an electroluminescent device. Analysis of the spectra from both photoluminescent and electroluminescent samples indicates that light passed through the metal film via surface-plasmon cross-coupling.; A theoretical model was used to analyze the interaction of dipolar molecules in the luminescent organic material with the structures evaluated in this research. This model showed that coupling to the surface plasmon supported by the organic/Ag interface was quite strong. Indeed, the model predicts that over 95% of the energy from a molecular dipole is emitted into the surface plasmon mode under optimal conditions, indicating that emission via surface-plasmon cross-coupling could be very efficient in an optimized device.; Both experimental and theoretical results indicate that surface-plasmon cross-coupling has great potential as a means of emission in organic light-emitting diodes and other electroluminescent devices. This mechanism could increase the external quantum efficiency of both organic and inorganic light-emitting diodes by reducing losses to guided modes. In addition, the possibility of emission through a metal allows the use of two metal electrodes, which could lead to higher electrical injection efficiency in electroluminescent devices. The application of this heretofore-unexploited physical process also expands the range of possible device structures for organic light-emitting diodes and other electroluminescent devices.