Abstract
An organic light emitting device is provided, including a first electrode; a flat layer formed on the first electrode; a light emitting layer which is formed and in contact with the flat layer so that the flat layer is sandwiched between the first electrode and the light emitting layer; and a second electrode which is formed and in contact with the light emitting layer so that the light emitting is sandwiched between the flat layer and the second electrode, wherein the light emitting layer includes co-host materials and light emitting materials so as to prolong the illumination time. The invention further provides methods for fabricating the organic light emitting device.