Forster energy transfer in combinatorial arrays of selective doped organic light-emitting devices

Energy transfer in highly-efficient doped organic light-emitting devices (OLEDs) is described and discussed. The OLEDs include a hole transport layer (HTL) and an electron transport layer composed of an efficient blue emitter. A region of the HTL adjacent to the host blue-emitting layer was doped with an efficient guest red dye. The blue emitter-to-red dye energy transfer probability P-HG(eta) was determined by comparing the emission from the two fluorophores and its dependence on the applied field. P-HG(eta) decreases with increasing field, probably due to an increasing fraction of dye molecules which are positively charged, i.e., which trap a hole. It is also estimated that at fields as low as 0.4 MV/cm, similar to50% of the dye emission is due to trap emission rather than Forster energy transfer. The analysis yields a Forster energy transfer radius R-0=33.5+/-3.5 Angstrom. (C) 2004 American Institute of Physics.