Solid State Thermochromic Materials

Solid-state thermochromic materials undergo semiconductor to metal transitions at a ‘critical temperature’, Tc. This review begins by describing the phenomenon of thermochromism, whereby the optical properties of a material change reversibly as a result of a change in temperature. The various different types of thermochromism will be introduced with a focus on the thermochromism exhibited by solid-state materials. The fundamental chemical principles that describe the electronic structure and properties of solids, and the chronological developments in the theory behind the thermochromic transitions (such as, the effects of electron-electron interactions and structural phase changes due to lattice distortions) that led to the discovery of the semiconductor-to-metal transition, are presented. An extensive discussion of vanadium and titanium oxides is presented with a particular focus on vanadium (IV) oxide since its transition temperature is closest to room temperature. Observations and c