Establishing the operational durability of polymer light-emitting diodes

This is the final report of a two-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). Recent research has made it clear that polymer light-emitting diodes (PLEDs) have all the necessary device attributes (efficiency, emission colors, operating voltage) required to build a successful display technology. This project was initiated to establish meaningful device operating lifetimes and to understand PLED failure mechanisms in order to control device reliability and ultimately produce a viable commercial product. A PLED lifetime testing capability was established to measure the change in PLED light output and drive voltage at constant current bias as a function of time for different current bias levels, operating temperatures and device (polymer) thickness. The dominant failure mechanism of the polymer light emitting diodes, occurring at less than 1000 hours of operation, was identified as delamination of the electron-injecting metal contact. A new electroabsorption technique to measure the electric field distribution inside the PLEDs was developed and then used to assess relative device reliability. 2 figs