photoinitiator

https://doi.org/10.1351/goldbook.14055
Agent initiating certain chemical transformations under the action of ultraviolet, visible, or infrared radiation and consumed therewith.
Note: A photocatalyst can also act as a photoinitiator that, however, will not be consumed.
Source:
PAC, 2011, 83, 931. (Glossary of terms used in photocatalysis and radiation catalysis (IUPAC Recommendations 2011)) on page 972 [Terms] [Paper]