Working Principles Electronic Properties of Organic Materials OLEDs active materials, i.e. materials producing light emission, are based on conjugated molecules and polymers or on organometallic compounds (composed by a metal coordinated by organic ligands). The active material must possess both good charge transport and emissive properties. Principles and Applications of Organic Light Emitting Diodes (OLEDs)explores the ways in which the development of organic semiconductor materials is opening up new applications in electronic and optoelectronic luminescent devices. The book begins by covering the principles of luminescence and the luminescent properties of organic semiconductors. The key point to operate OLEDs is to control the excitons (electron and hole pairs), so that holes and electrons meet in the emissive layer in equal quantities.9 HTL EML ETL Metal cathode Metal anode Glass Figure 3. The structure of OLEDs In Figure 4, the HOMO level of the molecules in the HTL is below the Fermi energy of the anode. Working Principle of LED. The working principle of the Light-emitting diode is based on the quantum theory. The quantum theory says that when the electron comes down from the higher energy level to the lower energy level then, the energy emits from the photon. The photon energy is equal to the energy gap between these two energy levels. In today's tutorial, we will have a look at Working Principle of LED. The full form of led is a light-emitting diode it is a diode that emits light when input supply is provided. It is semiconductor devices and like other diodes has PN junction. The emitting light from a diode depends on the energy needed by the bandgap of semiconductor The first organic light emitting diode with practical efficiency and brightness was demonstrated by Tang and Van Slyke working at Eastman Kodak in 1986.1 In the ensuing 30 years, OLEDs have been extensively optimised and today OLEDs are found in high end smartphone and televisions displays due to their superior display performance compared to LCDs. Even though organic light-emitting device (OLED) technology has evolved to a point where it is now an important competitor to liquid crystal displays (LCDs), further scientific efforts devoted to the design, engineering and fabrication of OLEDs are required for complete commercialization of this technology. Along these lines, the present work reviews the essentials of OLED technology putting Even though organic light-emitting device (OLED) technology has evolved to a point where it is now an important competitor to liquid crystal displays (LCDs), further scientific efforts devoted to the design, engineering and fabrication of OLEDs are required for complete commercialization of this technology. Along these lines, the present work reviews the essentials of OLED technology putting What is an OLED? An OLED is any light emitting diode in which organic layers are responsible for light emission. 6. The Basic Principal Electroluminescence is a process in which a material emits light in response to electrical field applied across it. 7. Cathode - The cathode injects electrons into emissive layer. OLED offers a drastically higher level of brightness and contrast as compared to LCD. The working principle and structure of OLED The OLED 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 ho