Luminescent mechanism of thermal effects in inorganic solids. (a) Emission from a luminescent activator upon excitation. (b) TQ results in nonradiative pathway associated with heat. (c) TI excites electrons to conduction band through heat. (d) TD can lead to other emissions as a result of heat. A and A* represent the ground and excited states of the activator, respectively. A’ and A*’ represent the ground and excited states of the activator with different charges, respectively. VB and CB represent the valence and conduction bands of the host, respectively.