colour centres

https://doi.org/10.1351/goldbook.14002
Lattice defects (typically vacancies) that trap one or more electrons or holes in ionic crystals. They constitute a long-lived deep trap with a low efficiency of trapping of a carrier of the opposite sign.
Notes:
  1. Colour centres accumulate in irradiated solids and give rise to photoinduced extrinsic absorption bands (photoinduced colour) in semiconductors and insulators. The dominant decay pathway of colour centres upon irradiation at moderate temperatures is photoionisation with the formation of free carriers and empty traps.
  2. The surface F (anion vacancies occupied by electrons) and V centres (trapped holes) in semiconductors and insulators are also colour centres with the distinction that they act as metastable active states of photocatalytic centres.
  3. Monitoring the photocolouration of a metal oxide during a surface photochemical reaction probes whether the reaction is photocatalytic.
See: energy trap
Source:
PAC, 2011, 83, 931. (Glossary of terms used in photocatalysis and radiation catalysis (IUPAC Recommendations 2011)) on page 945 [Terms] [Paper]
Citation: 'colour centres' 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.14002 RIS BibTex EndNote
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