Organic light-emitting display apparatus having optimized luminance by controlling thickness variation of emission layer

An organic light-emitting display apparatus comprising:

• a substrate;
• a first pixel electrode over the substrate, the first pixel electrode comprising an upper surface;
• a pixel defining layer covering an edge of the first pixel electrode, the pixel defining layer comprising a first opening exposing a portion of the first pixel electrode, the upper surface of the first pixel electrode being substantially planar throughout the first opening;
• and
• a first color emission layer disposed over the first pixel electrode and having an upper surface on which a distance in a direction perpendicular to a surface of the substrate between a highest point and a lowest point is about 400 Å to about 900 Å,
• wherein the lowest point on the upper surface of the first color emission layer overlaps the first opening, a distance from the substrate to the upper surface of the first color emission layer at a central portion of the first color emission layer is greater than a distance from the substrate to the upper surface of the first color emission layer at the lowest point of the first color emission layer, the first color emission layer comprises a valley, a distance from the substrate to the upper surface of the first color emission layer at the valley is less than the distance from the substrate to the upper surface of the first color emission layer at the central portion, and, in a plan view, the valley encloses the central portion of the first color emission layer.