A light emitting structure comprises a substrate, a plurality of sub-pixel stacks over the substrate emitting different colors, a bank surrounding the sub-pixel stacks and forming an interior space above the sub-pixel stacks, a first filler material in the interior space, a second filler material over the first filler material, and an interface between the first filler material and the second filler material. Each of the 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. The sub-pixel stacks each have a substantially uniform distance between the emissive layer and the first electrode layer. Each of the sub-pixel stacks emits a main emission peak at one direction normal to a top surface of each of the sub-pixel stacks through the interface.