fotoluminesenssikvanttihyötysuhde

Photoluminescence is a physical process where a substance absorbs photons and then re-emits photons. This re-emission typically occurs at a longer wavelength than the absorbed photons, meaning the emitted light has lower energy. The process involves exciting electrons within the material to higher energy levels. When these electrons return to their ground state, they release energy in the form of photons. The delay between absorption and emission can vary significantly, from picoseconds to hours.

There are several types of photoluminescence, distinguished by the time it takes for the emitted light to decay after the excitation source is removed. Fluorescence is a rapid form of photoluminescence where the emission ceases almost immediately, typically within nanoseconds. Phosphorescence is a slower process where the emitted light can persist for seconds, minutes, or even hours after excitation stops. This persistence is due to electrons being trapped in metastable states before eventually returning to the ground state.

Applications of photoluminescence are widespread. It is utilized in fluorescent lamps, where a gas discharge excites a phosphor coating that emits visible light. Fluorescent dyes are used in biological imaging and security features, while phosphorescent materials are found in glow-in-the-dark products. The study of photoluminescence is also crucial in understanding the properties of semiconductors and in developing new optical materials and technologies. The specific wavelengths absorbed and emitted, as well as the intensity and lifetime of the emission, provide valuable information about the electronic structure and chemical environment of the luminescent material.