KINETICS OF CHARGE-CARRIER RECOMBINATION IN ORGANIC LIGHT-EMITTING-DIODES

The temporal behavior of the electroluminescence (EL) from thin-film i ndium-tin-oxide (ITO)/aromatic diamine (TPD)/Al(III) s-hydroxyquinolin e (Alq(3))/Mg/Ag light-emitting diodes (LEDs) upon the application of a rectangular driving voltage is analyzed in terms of the electron-hol e recombination on the TPD/Alq(3) interface. From the long-time compon ent of the temporal decay of the EL intensity the electron-hole recomb ination coefficient gamma=(1.1+/-0.5)x10(-10) cm(3)/s is determined in good agreement with the value expected on the basis of the Langevin t heory of recombination with the recombination process controlled by th e motion of holes in the hole-transporting TPD layer of the LED. (C) 1 998 American Institute of Physics.