What is the Difference Between Photoluminescence and Electroluminescence?

Photoluminescence and electroluminescence are two types of luminescence, which is the emission of light by a substance that has not been heated. The key difference between the two lies in the mechanism that generates the light:

• Photoluminescence (PL): In this process, excess carriers (electrons and holes) are photo-excited by exposure to a sufficiently intense light, and the luminescence is emitted from the radiative recombination of these photo-excited carriers. The intensity and peak wavelength uniformity of photoluminescence can be acquired through mapping techniques.
• Electroluminescence (EL): In this process, excess carriers are produced by current injection, and the light is generated through the radiative recombination of these carriers. Electroluminescence is influenced by factors such as the optical properties of the material, the electrical properties of the two conductive regions used for cathode and anode contacts, and the properties of the electrical contacts through which the electrical current is injected.

Photoluminescence is mainly determined by the optical properties of the material, while electroluminescence is determined by a combination of optical and electrical properties. High photoluminescence efficiency is necessary but not sufficient for good electroluminescence; a wafer with high photoluminescence efficiency may or may not exhibit high electroluminescence. The different emission mechanisms between PL and EL can result in significant differences in their spectra, such as a small red-shift of the PL spectrum relative to the EL spectrum.

Comparative Table: Photoluminescence vs Electroluminescence

Here is a table comparing the differences between photoluminescence and electroluminescence:

Photoluminescence is a form of luminescence that occurs with a photoexcitation via photon absorption, where a substance absorbs electromagnetic radiation and re-emits the energy as light. Electroluminescence, on the other hand, is the emission of light due to the application of an electric field. In intrinsic electroluminescence, light is emitted when an electron recombines with an ionized atom of the crystal.