fotoelektronische

Fotoelektronische, or photoelectronic, refers to phenomena and devices that involve photoelectrons—electrons ejected or manipulated by light. In physics, the most well-known example is the photoelectric effect, where electrons are emitted from a material’s surface when illuminated with light that has sufficient energy. The effect provided crucial evidence for the quantum nature of light: photons with energy hν exceeding the material’s work function φ can liberate electrons, with kinetic energy roughly hν − φ. The emission rate depends on light intensity and frequency near the threshold, and measurable quantities include the photoelectric current and the stopping potential in vacuum experiments.

Historically, the effect was first observed by Hertz in 1887 and later explained quantitatively by Einstein in 1905, a breakthrough that contributed to quantum theory and earned the Nobel Prize in 1921. In solid-state contexts, external photoemission refers to electrons emitted into vacuum, while internal photoemission involves excitation within a material or across interfaces, both used to study work functions and electronic structure.

Applications of photoelectronic phenomena include photodetectors, photomultiplier tubes, and photocathodes for electron sources, as well as photoemission spectroscopy techniques (such as X-ray and ultraviolet photoelectron spectroscopy) used to characterize surface chemistry and electronic structure. The term encompasses a range of devices and methods that convert light into electronic signals or use light to probe the properties of materials, distinct from but related to photovoltaic concepts.