EFFICIENT BLUE-GREEN AND WHITE LIGHT-EMITTING ELECTROCHEMICAL-CELLS BASED ON POLY[9,9-BIS(3,6-DIOXAHEPTYL)-FLUORENE-2,7-DIYL]

Efficient blue-green polymer light-emitting electrochemical cells, bas ed on poly[9,9-bis(3,6-dioxaheptyl)-fluorene-2,7-diyl] (BDOH-PF), have been demonstrated. BDOH-PF has a high photoluminescent quantum effici ency of 73% photon/photon in solid films. The polyether-type side grou ps of this polymer are built in to promote the ionic conductivity nece ssary for the operation of light-emitting electrochemical cells (LECs) . Blue-green LECs using a blend of BDOH-PF and lithium triflate as the emissive layer, ITO and Al as the electrodes, achieve an external qua ntum efficiency of 4% photons/electron and a luminous efficiency of 12 Im/W at 3.1 V. The brightness reaches similar to 200 cd/m(2) at 3.1 V , and exceeds 1000 cd/m(2) at 3.5 V. When additional poly(ethylene oxi de) (PEO) is blended into the emissive layer, phase separation between PEO and BDOH-PF occurs, and the emission becomes white. These white e mitting LECs reach an external quantum efficiency of 2.4% photons/elec tron and 400 cd/m(2) brightness at a bias of 4 V. (C) 1997 American In stitute of Physics.