LIGHT-EMITTING ELECTROCHEMICAL-CELLS FROM A BLEND OF P-TYPE AND N-TYPE LUMINESCENT CONJUGATED POLYMERS

We demonstrate polymer light-emitting electrochemical cells (LECs) mad e of a blend of p- and n-type luminescent conjugated polymers. These t wo polymers, poly[9-(3,6,9-trioxadecyl)-carbazole-3,6-diyl] (TOD-PC, a p-type polymer) and poly[2,3-di(p-tolyl)-quinoxaline-5,8-diyl] (DT-PQ X, a n-type polymer), are blue and blue-green emission polymers, respe ctively, both with high photoluminescent quantum efficiency. However, the photoluminescence of the polymer blend is completely quenched, due to the charge transfer between the two polymers. A new and faint oran ge-yellow photoluminescence emission, which has photonic energy consis tent with the energy difference of the pi band of TOD-PC and the pi a nd of DT-PQX, has been observed. LECs fabricated from this polymer ble nd show strong current injection and bright electroluminescence at thi s new emission color, which is believed to be due to the interpolymer radiative recombination of the electrons from the n-type polymer and h oles from the p-type polymer. Such an independent p doping of TOD-PC a nd n doping of DT-PQX in the blend and interpolymer radiative recombin ation provide an interesting way of generating new emission colors in the LEC system. (C) 1997 American Institute of Physics.