Method for generating singlet oxygen by decomposition of endoperoxide molecules, wherein by means of a material system comprising at least two molecules and containing at least one molecule forming an endoperoxide group, an adjustment of a temporal progression of a decomposition of the endoperoxide molecules is made possible, wherein a molecule of the material system is a carrier material, wherein the carrier material is organic and has numerous molecules in its volume and provides a suitable microscopic and macroscopic structure, wherein the endoperoxide molecules are deposited on the surface of the carrier material or are incorporated in its interior, characterized in that adjusting of the temporal progression of the decomposition of the endoperoxide molecules is effected by a physical change in the functional structures present in the material system, wherein these functional structures each consisting of the endoperoxide-forming molecule and its immediate environment in the carrier material, namely a cage of the surrounding polymer matrix, wherein the physical change of a functional structure during the preparation comprises conducting a decomposition process after a procedure of endoperoxide formation, in which a change of the functional structure is caused by rearrangement processes, wherein the physical change of the functional structure comprises a change of the assembly position of the endoperoxide-forming molecule in the cage of the surrounding carrier material and/or a change of the cage or the cage wall, respectively; and after this preparation step, endoperoxide formation is executed again, yielding in a modified decomposition time which is attributable to the change of the barrier height for the decomposition associated with the geometric change in the functional structure. wherein by means of a material system comprising at least two molecules and containing at least one molecule forming an endoperoxide group, an adjustment of a temporal progression of a decomposition of the endoperoxide molecules is made possible, wherein a molecule of the material system is a carrier material, wherein the carrier material is organic and has numerous molecules in its volume and provides a suitable microscopic and macroscopic structure, wherein the endoperoxide molecules are deposited on the surface of the carrier material or are incorporated in its interior, characterized in that adjusting of the temporal progression of the decomposition of the endoperoxide molecules is effected by a physical change in the functional structures present in the material system, wherein these functional structures each consisting of the endoperoxide-forming molecule and its immediate environment in the carrier material, namely a cage of the surrounding polymer matrix, wherein the physical change of a functional structure during the preparation comprises conducting a decomposition process after a procedure of endoperoxide formation, in which a change of the functional structure is caused by rearrangement processes, wherein the physical change of the functional structure comprises a change of the assembly position of the endoperoxide-forming molecule in the cage of the surrounding carrier material and/or a change of the cage or the cage wall, respectively; and after this preparation step, endoperoxide formation is executed again, yielding in a modified decomposition time which is attributable to the change of the barrier height for the decomposition associated with the geometric change in the functional structure. <EOS>