A device is provided, having an anode, a cathode, and a first organic layer disposed between the anode and the cathode. The first organic layer comprises a material that produces phosphorescent emission when a voltage is applied between the anode and the cathode. A second organic layer is disposed between the first organic layer and the cathode. The second organic layer is in direct contact with the first organic layer. The second organic layer may comprise an aromatic hydrocarbon material, comprising an aromatic hydrocarbon core optionally substituted, and wherein the substituents are the same or different, and each is selected from the group consisting of alkyl, aryl, heteroalkyl, substituted aryl, substituted heteroaryl and heterocyclic groups. The second organic layer may comprise a material having a dipole moment less than about 2.0 debyes, such that the device has an unmodified external quantum efficiency of at least about 3% and a lifetime of at least about 1000 hours at an initial luminance of about 100 to about 1000 cd/m
2
. The second organic layer may be in direct contact with the cathode, or there may be a separate organic layer between the second organic layer and the cathode.
该设备包括一个阳极、一个阴极和一个第一有机层,该第一有机层位于阳极和阴极之间。第一有机层包括一种材料,当在阳极和阴极之间施加电压时,该材料产生
磷光发射。第二有机层位于第一有机层和阴极之间,且与第一有机层直接接触。第二有机层可以包括一个芳香族碳氢化合物材料,包括一个芳香族碳氢核心,该核心可以选择性地被取代,且取代基相同或不同,每个取代基选自烷基、芳基、杂原子烷基、取代芳基、取代杂原子芳基和杂环基组成的群。第二有机层可以包括一个具有偶极矩小于约2.0德拜的材料,使得该设备具有至少约3%的未修改外部量子效率和在初始亮度约100到约1000 cd/m2时至少约1000小时的寿命。第二有机层可以直接接触阴极,或者第二有机层和阴极之间可以有一个单独的有机层。