Polymer organic light emitting device with improved color control

An OLED[100, 200, 300] for emitting light at a predetermined peak wavelength, λ. The OLED[100, 200, 300] includes an anode layer[106, 206], a cathode layer[112, 212] and an electroluminescent layer[110, 210] constructed from an organic light emitting compound that generates light, including light having a wavelength equal to λ, by the recombination of holes and electrons. The electroluminescent layer[110, 210] is electrically connected to the anode layer[106, 206] and the cathode layer[112, 212] and is located between the anode and cathode layers. The OLED[100, 200, 300] includes a first reflector[104, 202] and second reflector, displaced from one another. The anode layer[106, 206] or cathode layer[112, 212] can serve as one of the reflectors. A spacer layer[108, 208, 220] constructed from a material that is transparent at λ is included between the reflectors and has a thickness that is adjusted such that the optical path length between the first and second reflectors is equal to Nλ/2, where N is a positive integer. The spacer[108, 208, 220] may include a hole transport material located between the electrolumniscent layer[110, 210] and the anode layer. The spacer[108, 208, 220] may also be constructed from a layer that is located between the anode or cathode layers and one of the reflectors. If the spacer layer[108, 208, 220] is located between the anode and cathode layers, the spacer layer[108, 208, 220] is constructed from an electrically conducting material.