How does heat release trapped electrons in thermoluminescence?

In thermoluminescence, electrons are captured and immobilized in traps—imperfections within a crystal lattice—following exposure to high-energy radiation. These traps are intentionally created or exist as defects, and they are characterized by a "trap depth," which represents the minimum thermal energy required to release a trapped charge.123

At room temperature, this trap depth is typically large enough that the rate of detrapping is negligible, allowing the electrons to remain stored for long periods. When the material is heated, the added thermal energy provides the necessary stimulus to eject the trapped electrons from these imperfections. Once liberated, the electrons are raised to the conduction band, where they can move freely until they recombine with a remaining trapped hole (or vice versa). This recombination process results in the release of energy in the form of a photon within the visible part of the electromagnetic spectrum.243