Polymer bulk homojunction light-emitting electrochemical cells

Abstract

We report polymer light-emitting electrochemical cells (LECs) based on the in situ formation of thousands of micrometer-sized light-emitting p-n junctions within the bulk of the device. These "bulk homojunction" LECs, achieved by mixing metallic particles into the LEC film, exhibit dramatically improved electroluminescence (EL) output and response time. This is confirmed by EL intensity and absolute luminance measurements, which reveals an increase in quantum efficiency of more than tenfold, relative to a conventional single junction LEC of similar dimensions. The high performance of a bulk homojunction is attributed to its large specific emitting area. Further, we demonstrate red-, green-, and blue-emitting bulk homojunction LECs by using various combinations of luminescent polymers and metallic particles. © 2006 American Institute of Physics.