Composition

A layer comprising at least a matrix material and one or more light emitting moieties, wherein the distribution of the light emitting moiety in the layer is not identical in the direction of layer thickness.

A layer containing at least a matrix material and one or more emitting moieties, contains a 1st phase and a 2nd phase, wherein said 1st phase and said 2nd phase are different of each other and said 1st phase has a plurality of aggregates of said light emitting moieties and higher concentration of the light emitting moieties per unit volume in the 1st phase than in the 2nd phase.

A layer containing at least a matrix material and one or more emitting moieties, wherein 30 wt. % or more of the light emitting moieties based on the total amount of the light emitting moieties in the layer are concentrated in an area of the layer, wherein said area has the thickness within 25% of the thickness of the layer.

A layer containing at least a matrix material and one or more emitting moieties, wherein 41 wt. % or more of the light emitting moieties based on the total amount of the light emitting moieties in the layer are concentrated in the area of the layer, wherein said area has the thickness within 40% of the layer thickness of the layer.