DIRECT DETERMINATION OF THE EMISSION ZONE IN A POLYMER LIGHT-EMITTINGDIODE

Many operating mechanisms of polymer light-emitting diodes (LEDs) are still not fully understood, among them the crucial step of recombinati on of oppositely charged carriers to form excitons. Questions related to this step are: What is the shape of the recombination zone and what is the quenching loss at the metal electrode layers? An investigation is reported in which the emission zone is directly determined by anal yzing the polarization of the electroluminescence. It is shown that ex citon quenching near the electrodes is a crucial parameter for the ove rall device efficiency.