Exciplex emission in conjugated polymer light-emitting devices.

摘要

Extensive studies have been completed on photoluminescence and electroluminescence of pyridine based polymers and copolymers. Differences in the photoluminescence in solutions and films can be explained through torsion angle calculations and aggregation in the films. Bilayers of our pyridine based copolymers and poly(vinyl carbazole) (PVK) show a PL peak which cannot be ascribed to either the copolymer or the PVK. Through studies of absorption, photoluminescence excitation (PLE) and PL, we demonstrate that the additional feature results from an exciplex at the bilayer interface. In addition, we see exciplex emission from blends of copolymers with PVK.; Light emitting devices were fabricated in a variety of configurations. The brightest and most efficient devices were made using a bilayer configuration with a strapped copolymer poly(pyridyl vinylene phenylene vinylene) and PVK, making use of the exciplex emission at the interface. The devices typically had a brightness greater than 250 cd/m{dollar}{bsol}sp2{dollar} with efficiencies from 0.1% to 0.5%. The bilayer configuration also moves the emission center of the device away from the electrodes, which quench the luminescence. In addition to bilayer devices many other device configurations were developed. Symmetrically configured AC light emitting (SCALE) devices emit light under both forward and reverse bias as well as under an ac bias. Inverted devices use stable high work function electrodes. Through the use of polyaniline based network electrodes the turn-on voltages of single and bilayer device was significantly reduced without loss of brightness or efficiency. The current-voltage characteristics are understood in terms of space charge limited current and tunneling theory.; Polymer/polymer and polymer/metal interfaces are a key issue in understanding all of the results involving the devices as well as the luminescence of these systems. In the bilayer and SCALE devices, the interfaces act to improve and/or alter device performance. The nature of the polymer/metal interfaces also plays an important role in both single and multilayer devices.