Title: free electrons
Long Title: IUPAC Gold Book - free electrons
DOI: 10.1351/goldbook.14015
Status: current

Definition
Photoexcited electrons from the valence band into the conduction band in semiconductors and insulators.

Notes
1) Thermoexcitation or doping with certain impurities also leads to formation of free electrons in the conduction band of semiconductors. In metals and n-type semiconductors free electrons exist originally.
2) The expression "free electron carrier" is redundant and not recommended.

Source
- PAC, 2011, 83, 931. 'Glossary of terms used in photocatalysis and radiation catalysis (IUPAC Recommendations 2011)' on page 954 (https://doi.org/10.1351/PAC-REC-09-09-36)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/14015/html
- json: https://goldbook.iupac.org/terms/view/14015/json
- xml: https://goldbook.iupac.org/terms/view/14015/xml

Citation: Citation: 'free electrons' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.14015
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Accessed: 2026-06-22T10:12:31+00:00