Much like any LED, it consists of layers of conductive materials sandwiched between an anode and cathode. In an OLED, however, the emissive layer is comprised of organic compounds. When a voltage is applied across the cathode and anode, current begins to flow. The cathode supplies negatively charged electrons, while the anode supplies positively charged holes — imaginary particles which represent the absence of an electron.

The different layers in the OLED help to efficiently transport the electrons and holes towards the emissive layer, where they recombine. When this electron-hole recombination occurs, an exciton is formed and a photon is emitted. The wavelength, or color, of this photon is determined by the specific organic compounds found in the emissive layer.

In a typical bottom-emitting OLED, such as the one pictured to the right, the OLED is fabricated by depositing layers of conductive materials on a glass or plastic substrate. This substrate is typically pre-coated with Indium-Tin-Oxide (ITO) which operates as the transparent anode component of the diode. Glass pre-coated with ITO is readily and cheaply available, as it is a key component in LCD panel fabrication.

Next, the Hole-Transport Layer (HTL) is deposited, which enhances the ability of the anode to deliver holes. In some configurations, an additional Hole-Injection Layer (HIL) is deposited in addition to the HTL to further optimize hole delivery and exciton formation in the emissive layer.

The Emissive Layer (EML) is where the electron-hole recombination takes place. The organic compounds found in this layer determine the color of light emitted by the OLED. For example, the small molecule compound Alq3 [tris(8-hydroxyquinoline) Aluminum] emits green light.

The Electron-Transport Layer (ETL) optimizes the transport of electrons from the cathode to the emissive layer. In simpler configurations, the EML also serves as an ETL.