High on-axis brightness and low colour shift QD-LED pixel with equal layer thicknesses between colour pixels

A sub-pixel structure comprising:

• a plurality of sub-pixel stacks emitting different colors, each of the plurality of sub-pixel stacks including an emissive layer between a first transport layer and a second transport layer, a first electrode layer coupled to the first transport layer, and a second electrode layer coupled to the second transport layer;
• a bank surrounding each of the plurality of sub-pixel stacks and forming an interior space above each of the plurality of sub-pixel stacks;
• a first filler material in the interior space and having a first refractive index;
• a second filler material over the first filler material and having a second refractive index lower than the first refractive index;
• and
• an interface between the first filler material and the second filler material,
• wherein:
• the plurality of sub-pixel stacks has a substantially uniform distance between the emissive layer and the first electrode layer;
• at least one of the plurality of sub-pixel stacks is configured to emit light in a plurality of wavelengths having a central wavelength;
• the distance between the emissive layer and the first electrode layer is predefined so that at least one of the plurality of sub-pixel stacks emits a main emission peak into the filler materials along an on-axis direction substantially normal to a top surface of the at least one of the plurality of sub-pixel stacks;
• the main emission peak emitted through the interface from the at least one of the plurality of sub-pixel stacks has a minimum of light reflected by total internal reflection over all pixels;
• and
• in the at least one of the plurality of sub-pixel stacks, a phase shift associated with an emission from the emissive layer to the first electrode and back to the emissive layer is 2π.

A sub-pixel structure comprising:

• a plurality of sub-pixel stacks emitting different colors, each of the plurality of sub-pixel stacks including an emissive layer between a first transport layer and a second transport layer, a first electrode layer coupled to the first transport layer, and a second electrode layer coupled to the second transport layer;
• a bank surrounding each of the plurality of sub-pixel stacks and forming an interior space above each of the plurality of sub-pixel stacks;
• a first filler material in the interior space and having a first refractive index;
• a second filler material over the first filler material and having a second refractive index lower than the first refractive index;
• and
• an interface between the first filler material and the second filler material,
• wherein:
• the plurality of sub-pixel stacks has a substantially uniform distance between the emissive layer and the first electrode layer;
• at least one of the plurality of sub-pixel stacks is configured to emit light in a plurality of wavelengths having a central wavelength;
• the distance between the emissive layer and the first electrode layer is predefined so that at least one of the plurality of sub-pixel stacks emits a main emission peak into the filler materials along an on-axis direction substantially normal to a top surface of the at least one of the plurality of sub-pixel stacks;
• the main emission peak emitted through the interface from the at least one of the plurality of sub-pixel stacks has a minimum of light reflected by total internal reflection over all pixels;
• and
• in at least another of the plurality of sub-pixel stacks, a phase shift associated with an emission from the emissive layer to the first electrode and back to the emissive layer is either less than 2π or greater than 2π, resulting in a change in brightness in a main emission peak.