Photochemical control of dark conductivity - a new approach to devices based on molecular crystals

Thermal analysis of Ag(DM)2, where DM=2,5-dimethyl-N,N’-dicyanoquinonediimine, clarified that the salt had an insulating amorphous phase (≥155°C). Characterization of this and related solid states of Ag(DM)2 indicated that a photo-induced process should be essential in controlling the number of carriers and thus conduction behavior of the salt by illumination. In fact, while heating could do nothing but make the salt insulating when the sample temperature exceeded 155°C, ultraviolet-visible light illumination (<155°C) could gradually change the properties to be semiconducting with retaining the crystal lattice (average structure).