Organic light emitting device which emits white light

An organic light emitting device which emits white light, comprising:

• a reflective anode,
• a first light emitting layer which emits red light located over said reflective anode,
• a second light emitting layer which emits blue light and green light located over said first light emitting layer, and
• a cathode structure located over said second light emitting layer comprising:
• a first semi-reflecting semi-transparent layer;
• and
• a second semi-reflecting semi-transparent layer with a layer of light transmissive material between the first and second semi-reflecting semi-transparent layers,
• wherein a first distance between the reflective anode and the first semi-reflecting semi-transparent layer is selected to form a first micro-cavity which enhances blue light emission and red light emission from the organic light emitting device, and
• wherein a second distance between the reflective anode and the second semi-reflecting semi-transparent layer is selected to form a second micro-cavity which enhances green light emission from the organic light emitting device.