Light emitting device with tuned cathode layer optical properties

摘要

A light emitting device 300 comprising: a light transmissive first electrode 304; a light emitting layer 306; and a second electrode 308 comprising a light absorbing layer layer with a complex refractive index RI = n + i.k, where the value of n (the refractive index) lies between 1.3 and 2.2 and the value of k (the extinction coefficient) lies between 0.05 and 0.5. The second electrode 308 may be light absorbing layer or the light absorbing layer may be a further layer disposed on a separate second electrode 308. The light absorbing layer may comprise a combination of metallic particles and a host, where the metallic particles may be silver or copper and where the host may be a metal oxide, such as zinc oxide or indium tin oxide; or a conductive polymer, such as a fluorene polymer or copolymer, PEDOT:PSS or thiophene polymer or copolymer (e.g. F8-BT). The silver particles may be part of a silver colloid having a ratio of 3:7 silver to polycarbonate. The second electrode 308 may be a cathode and have a reflectivity of less than 2%.