[absolutezero]

Hello! I was wondering if there are any chemicals or chemical compounds - organic or inorganic - that go from transparent to blocking light by running an electric current through them, similar to liquid crystal technology. This change can be permanent or temporary. Thank you!

[Dude]

Liquid crystal technology is based mostly upon organic chemicals.  An example of one is cholersteryl myristate (ester of cholesterol + myristic acid).  The term "liquid crystal" refers to a phase in between the solid state and liquid state that has some order, but is not ordered (solid) or disordered (liquid).  Molecules that have this phase usually have some polarity (to respond to the electric field) and rigidity (to cause the scattering or change in refractive index).  It is only in this phase that liquid crystals are electrically active.  Heating above it or below it and the molecule doesn't orient significantly with the electric field.  Check out the book by Peter Collings on Liquid Crystals.  It is pretty easy to read.  There might be some inorganic materials, however, I would guess the response is smaller due to the energy change needed to reorient a solid crystal.

[Mitch]

Yes do google searches for either organic or inorganic optoelectronic switches.