NOVEL-APPROACH FOR HOLE-BLOCKING IN LIGHT-EMITTING ELECTROCHEMICAL-CELLS

The light emission from solid-state conjugated polymer light-emitting electrochemical cells (LECs) has been studied when a hole-blocking lay er was employed. A multilayer LEC consists of an indium-tin oxide (ITO ) electrode, an emissive (EM) layer of poly(1,4-phenylenevinylene) (PP V) containing poly(ethylene oxide) (PEG) complexed with lithium triflu oromethanesulfonate, a hole-blocking (HE) layer of PEO complexed with poly(lithium 4-styrenesulfonate) (PSS-LI), and an aluminum (Al) electr ode. The light emission intensity and external quantum efficiency of I TO/EM/HB/EM/Al cells were clearly greater than those of ITO/EM/Al cell s. These results indicate that holes on the PPV main chain are trapped by immovable PSS anions and that the HE layer is effective for improv ing light-emitting properties of LECs. (C) 1997 Elsevier Science S.A.