An organic light emitting diode (OLED) emitting light downward through a transparent substrate. The OLED embeds a microcavity formed between a cathode and an anode and includes a plurality of organic layers including a light emitting layer. The plurality of organic layers include at least a first layer made of an organic doped material aimed at enhancing the transport of electrons; and at least a second layer made of an organic doped material aimed at enhancing the transport of holes. The anode is obtained by deposition of a semitransparent layer of silver (Ag) over the transparent substrate to be directly in contact with the first doped organic layer. Then, thicknesses of the first and second doped organic layers can be freely adapted to best adjust the optical characteristics of the microcavity for the wavelength of monochromatic light to be produced by the OLED.