Encyclopedia … combined with a great Buyer's Guide!

Phosphorescence

Author: the photonics expert

Definition: a luminescence which lasts for a relatively long time after excitation of a medium

More general term: luminescence

Category: article belongs to category physical foundations physical foundations

DOI: 10.61835/m6g   Cite the article: BibTex plain textHTML   Link to this page   LinkedIn

Phosphorescence is a kind of luminescence (i.e., a kind of light emission of a medium) which lasts relatively long after excitation of the medium with light (for example many milliseconds or more). The excitation energy is stored in metastable electronic states (often triplet states reached via intersystem crossings), exhibiting only forbidden transitions to lower states. There are also cases with delayed fluorescence, where one has an intersystem crossing to a triplet state and later on back to the original singlet state. Very long decay times can also occur due to thermally activated delayed fluorescence (TADF), where an involved thermal excitation is very slow because of an energy gap much larger than <$k_\textrm{B} T$>. Some authors would not call that phosphorescence, although it is common to call certain substances phosphorescent where such traps play a vital role.

As the stored energy can be released only through relatively slow processes, phosphorescence is generally much weaker than fluorescence.

Important phosphorescent materials are europium-doped strontium aluminate (Eu2+:SrAl2O4) and zinc sulfide (Eu2+:ZnS). They are used e.g. in safety products such as exit signs, which are visible even under conditions of power failure, although they are not very bright. Phosphorus, from which the name phosphorescence was originally derived, actually exhibits chemoluminescence.

Fluorescent lamps also exhibit a low level of phosphorescence (an afterglow) of the phosphor for some time after being switched off.

More to Learn

Encyclopedia articles:

Questions and Comments from Users

Here you can submit questions and comments. As far as they get accepted by the author, they will appear above this paragraph together with the author’s answer. The author will decide on acceptance based on certain criteria. Essentially, the issue must be of sufficiently broad interest.

Please do not enter personal data here. (See also our privacy declaration.) If you wish to receive personal feedback or consultancy from the author, please contact him, e.g. via e-mail.

Spam check:

By submitting the information, you give your consent to the potential publication of your inputs on our website according to our rules. (If you later retract your consent, we will delete those inputs.) As your inputs are first reviewed by the author, they may be published with some delay.

preview

Share this with your network:

Follow our specific LinkedIn pages for more insights and updates: