Term: delayed luminescence
https://doi.org/10.1351/goldbook.D01580

Definition:
luminescence decaying more slowly than that expected from the rate of decay of the emitting state. The following mechanisms of luminescence provide examples:triplet-triplet or singlet-singlet annihilation to form one molecular entity in its excited singlet state and another molecular entity in its electronic ground state (sometime referred to as P type),  thermally activated delayed fluorescence involving reversible intersystem crossing (sometimes referred to as E type), and   combination of oppositely charged ions or of an electron and a cation. For emission to be referred to in this case as delayed luminescence at least one of the two reaction partners must be generated in a photochemical process.

Related Terms:
1) delayed fluorescence (http://doi.org/10.1351/goldbook.D01579).
2) luminescence (http://doi.org/10.1351/goldbook.L03641).
3) singlet-singlet annihilation (http://doi.org/10.1351/goldbook.S05697).
4) singlet state (http://doi.org/10.1351/goldbook.S05699).
5) ground state (http://doi.org/10.1351/goldbook.G02704).
6) thermally activated delayed fluorescence (http://doi.org/10.1351/goldbook.T06305).
7) intersystem crossing (http://doi.org/10.1351/goldbook.I03123).
8) cation (http://doi.org/10.1351/goldbook.C00907).

Source: PAC, 1988, 60, 1055. 'Glossary of terms used in photochemistry (Recommendations 1988)' on page 1065 (https://doi.org/10.1351/pac198860071055)

Citation: 'delayed luminescence' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.D01580

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