fotoluminescentiekwantumopbrengst

Fotoluminiscencia, or photoluminescence, is the emission of light by a material after it absorbs photons. The process begins when a substance absorbs energy, promoting electrons to higher electronic states, and ends with the release of part of that energy as photons as the system relaxes to lower energy states. Photoluminescence occurs without the need for external electrical current and is driven by optical excitation.

Two primary forms are fluorescence and phosphorescence. In fluorescence, emission occurs rapidly, typically within nanoseconds, and ceases soon after the excitation stops. In phosphorescence, emission can persist after excitation due to population of long-lived triplet states, producing an afterglow that can last microseconds to hours.

Mechanistically, after absorption a molecule undergoes vibrational relaxation to the lowest excited singlet state (S1). Radiative decay from S1 to the ground state (S0) yields fluorescence. If intersystem crossing to a triplet state (T1) occurs, phosphorescence may follow, with longer lifetimes. Non-radiative pathways, such as vibrational coupling or environmental quenching, compete with emission and influence efficiency.

Materials that exhibit photoluminescence include organic dyes and polymers, inorganic phosphors, quantum dots, and perovskite-based systems. Photoluminescent properties depend on factors such as chemical composition, concentration, temperature, and the surrounding matrix or solvent, which can affect quantum yield and lifetime.

Applications span lighting and displays (LEDs and OLEDs), fluorescent labeling and bioimaging, chemical and biological sensing, security inks, and solar-energy devices like luminescent solar concentrators. Key performance metrics include emission wavelength, quantum yield, luminescence lifetime, and photostability.