OLED Emitting Layer Stack for Narrow FWHM and High Efficiency

The emitting material layer is segmented into multiple distinct layers: a first emitting layer containing delayed fluorescent material, a second emitting layer containing fluorescent material, and a third emitting layer containing phosphorescent material. Each layer has specific thickness ranges (5-50 nm, 5-30 nm, and 5-20 nm respectively) and is positioned at different depths from the first electrode. This segmentation allows each material type to contribute its strengths while minimizing individual weaknesses, achieving narrow FWHM through the fluorescent layer's contribution while maintaining high efficiency through the delayed fluorescent and phosphorescent layers.

The second emitting layer containing fluorescent material acts as an intermediary between the first emitting layer (delayed fluorescent) and the third emitting layer (phosphorescent). This intermediate fluorescent layer helps manage energy transfer and reduces direct interaction between the delayed fluorescent and phosphorescent materials, thereby minimizing thermal degradation and non-emission quenching effects while preserving the high emitting efficiency benefits of the delayed fluorescent material.

Instead of combining multiple emitting materials in a single horizontal plane, the invention transitions to a vertical dimensional arrangement with three distinct emitting layers stacked sequentially from the first electrode. Each layer has controlled thickness (5-50 nm for first layer, 5-30 nm for second layer, 5-20 nm for third layer) and specific compositional ratios. This vertical stratification simplifies the horizontal structure while maintaining the benefits of multiple material combinations, and allows independent optimization of each layer's properties.