A very high-contrast top-emitting organic light-emitting diode with a Ni/ZnS/MgF₂/Ni contrast-enhancing stack and a CuPc/C60 anti-reflection bilayer

A top-emitting organic light-emitting diode (TEOLED) with a very low luminous reflectance of 1.66% and very high contrast ratios of 405.9:1 and 1350.6:1 under on-state luminance of 300 and 1000 cd/m² is fabricated by using a Ni/ZnS/MgF₂/Ni contrast-enhancing stack (CES) and a copper-phthalocyanine (CuPc)/C60 anti-reflection (AR) bilayer. Although the introduction of the CES structure, it almost does not influence electrical performances of devices and a high luminance is obtained in TEOLED by using light output CuPc/C60 bilayer. The working mechanism on the reduced reflectance in high contrast TEOLED is further explored. Research shows that very low reflectance is attributed to both the effective absorption of C60 and CuPc and a destructive interference to the ambient light.