Electroluminescent devices with improved optical out-coupling efficiencies

An organic electroluminescent device, comprising:

• an optically reflective concave structure, comprising:
• a first optically reflective surface;
• and
• a second optically reflective surface, intersecting said first optically reflective surface at an obtuse angle;
• a first light propagation layer in direct contact with said first optically reflective surface and said second optically reflective surface, comprising:
• a first refractive surface, parallel to and separated from said first optically reflective surface;
• a second refractive surface, parallel to and separated from said second optically reflective surface;
• and
• an electroluminescent area, disposed entirely within said first light propagation layer, between said first optically reflective surface and said first refractive surface, without directly contacting any of said first optically reflective surface, said second optically reflective surface, said first refractive surface and said second refractive surface;
• and
• a second light propagation layer, disposed on the first light propagation layer, wherein said second light propagation layer has a greater refractive index than said electroluminescent area minus 0.2.