The present invention relates to monochromatic organic light emitting devices. The organic light emitting device includes a substrate, an anode, a cathode and an organic electroluminescent medium disposed between the anode and the cathode, wherein the organic electroluminescent medium includes compound monochromatic luminescent layer; and the compound monochromatic luminescent layer includes host A doped with monochromatic dopant and host B doped with monochromatic dopant, wherein the host A is consisted of two kinds of materials with different transporting characteristics, one is hole-transporting material, and the other is electron-transporting material. In addition, the present invention further relates to white organic light emitting devices, wherein the organic electroluminescent medium is consisted of at least one compound monochromatic luminescent layer, which includes host A doped with monochromatic dopant and host B doped with monochromatic dopant. The present invention provides a design to improve the lifetime of the organic light emitting device markedly.