MoO3 as combined hole injection layer and tapered spacer in combinatorial multicolor microcavity organic light emitting diodes

Multicolor microcavity (μC) organic light-emitting diode (OLED) arrays were fabricated simply by controlling the hole injection and spacer MoO3 layer thickness. The normal emission was tunable from ∼490 to 640 nm and can be further expanded. A compact, integrated spectrometer with two-dimensional combinatorial arrays of μC OLEDs was realized. The MoO3 yields more efficient and stable devices, revealing a new breakdown mechanism. The pixel current density reaches ∼4 A/cm2 and a maximal normal brightness ∼140 000 Cd/m2, which improves photoluminescence-based sensing and absorption measurements.