一种改善红光顶发射OLED色纯度及角度依赖特性的方法研究

在Si/SiO₂衬底上生长金属银作为阳极,4,4,4-tris(3-methylphenylpheny-lamino)-triphenylamine(m-MTDATA):MoOx/m-MTDATA/N,N-bis-(1-naphthyl)-N,N-diphenyl-1,1-biphenyl-4,4-diamine(NPB)作为空穴注入及传输层,发光层采用4,4-N,N-dicarbazole-biphenyl(CBP)掺杂磷光染料(1-(phenyl)isoquinoline)iridium(III) acetylanetonate(Ir(piq)₂(acac))的结构,4,7-di-phenyl-1,10-phenanthroline(BPhen)作为空穴阻挡层及电子传输层,阴极为LiF(1 nm)/Al(2 nm)/Ag(20 nm)复合阴极结构.通过在光取出的复合阴极上方生长一层CBP光学覆盖层,有效地改善了复合阴极膜系的透射率,从而改善了顶发射结构的光学耦合输出特性,在提高器件的正向发光效率的同时还使色坐标往深红光区移动.并且生长光学覆盖层结构的器件角度依赖特性明显得到改善,这对于制作高显示质量的显示器件具有重要意义.在原有结构的基础上增加20 nm的NPB掺杂磷光染料Ir(piq)₂(acac)作发光层,从而得到双发光层结构为NPB:Ir(piq)₂(acac)(1%,20 nm)/CBP:Ir(piq)₂(acac)(1%, 20 nm).由于NPB具有较高的空穴迁移率,避免了由于光学厚度的增加而引起器件工作电压的大幅升高,而双发光层的结构有利于增大激子复合区域,提高辐射复合几率,减少非辐射损耗,实现主客体之间高效的三线态能量传递,相对单发光层顶发射结构,双发光层结构不仅提高了器件的发光效率,而且改善了器件的色坐标.

A Method for Improving the Color Purity and Angle-dependent Character of Red Top-emitting Organic Light-emitting Device

Ag was deposited onto Si/SiO₂ substrate as anode, 4,4,4-tris(3-methylphenylpheny-lamino)-triphenylamine(m-MTDATA):MoO_x/m-MTDATA/N,N-bis-(1-naphthyl)-N,N-diphenyl-1,1-biphenyl-4,4-diamine(NPB) were used as hole-injected layer and hole-transporting layer,respectively. 4,4-N,N-dicarbazole-biphenyl(CBP) doped with (1-(phenyl)isoquinoline) iridium (III) acetylanetonate(Ir(piq)₂(acac)) was chosed as emitting layer. 4,7-di-phenyl-1,10-phenanthroline(BPhen) worked as hole-blocking layer and electronic-transporting layer. LiF(1 nm)/Al(2 nm)/Ag(20 nm) were composite cathode. In order to improve the outcoupling character of the top-emitting device, an organic CBP layer was introduced above the cathode. Appropriate use of the optical outcoupling layer is helpful for improving the transmittance of the composit cathode film system, and caused the color of the emitting light moved to deep-red region. The angle-dependent properties of the devices were also investigated and the ones with optical outcoupling layer show better performance. And it is very meaningful to the production of high-quality displays. In further study, another 20 nm NPB doped with Ir(piq)₂(acac) was introduced to form dual emitting-layer structure, and while the driving voltage of the devices did not significant increase due to the relative high hole mobility of NPB. Meanwhile efficient triplet energy transfer between the host and guest is obtained, the recombination zone is broadened and the non-radiative losses is reduced, seen from the experimental, the current efficiency and color purity are both improved for the dual emitting-layer devices compared with the single emitting-layer structures.