The working principle and structure of OLED

The SMOLED/PLED is analogous to that of conventional light-emitting diodes in terms of the working principle. The light emission is through the recombination of electrons and holes from the cathode and anode, respectively. Depending on the device structure, a typical OLED has a hole transport layer (HTL), emitting material layer (EML), and electron transport layer (EML) in between the electrodes. A current injection through the device excites the electrons to higher energy states, and their relaxation to lower states results in light emission with the wavelengths depending on the organic materials and device structure used.