Charge separation in solar cells

[Stanley514]

If there is a charge separation on macroscale in a solar cells (electrons flow in one direction and holes in another) why there is no high voltage build up similar to capacitors or piezoelectrics where also charge separation occur?

There exist some glasses which become conducting when heated over 300°C. Most of them become ionic conductors but some possibly electronic.
If we will heat them with pulses of heat so they will periodically turn to conducting state and back,
could we convert heat to electricity with charge separation similar to solar cell?

 

[BigJDubs]

In theory, it is possible to convert heat into electricity using a material that can periodically turn between a conducting and nonconducting state. However, this process is not as efficient as solar cells, and it would require a lot of energy to be able to generate a significant amount of electricity. Additionally, it is unlikely that the charge separation resulting from the periodic heating of the material would be enough to generate a high voltage output, as in the case of capacitors or piezoelectrics.