Light-dependent ionic-electronic conduction in an amorphous octahedral molybdenum cluster thin film

Abstract

We developed a new environment-sensing device based on the opto-ionic-electronic phenomena of an octahedral molybdenum metal (Mo6) cluster. When the Mo6 cluster is electrochemically deposited on a transparent electrode in an organic solvent containing a trace amount of water, the water permeates the deposited film. During the process, some ligand species that stabilize the frame structure of the Mo6 cluster are substituted with hydroxyl groups, and the negatively charged frame structure of the Mo6 cluster unit is stabilized by hydronium counterions. As a result, the transparent film of the Mo6 cluster fabricated by this method exhibits ionic-electronic mixed conduction of the hydronium ion. The ionic conduction greatly changes depending on the temperature and humidity in the atmosphere, and the electrical conductivity greatly changes depending on the wavelength and intensity of the irradiated light. These unique multisensing properties present new possibilities for environmental sensing applications.