  Non-equilibrium charge dynamics, such as cooling-rate-dependent charge
vitrification and physical aging, have been demonstrated for a charge-cluster
glass in $\theta$-(BEDT-TTF)$_2$CsZn(SCN)$_4$ using electron transport
measurements. The temperature evolution of the relaxation time obeys the
Arrhenius law, indicating that the glass-forming charge liquid can be
classified as a "`strong" liquid in the scheme of canonical structural-glass
formers. X-ray diffuse scattering further reveals that the spatial growth of
charge clusters in the charge liquid is frozen below the glass transition
temperature, indicating an intrinsic relationship between dynamics and
structure in the charge-cluster glass.
