Why couldn't you collect the solar energy from the outside of the window and put up blinds to block the light from the inside of the window? Putting up blinds won't generate any electricity.

What if we could design a solar cell that could shift from transparent to opaque on demand? Instead of putting up blinds, simply move a slider or tap a button or what have you, and suddenly the amount of light coming in is dimmed, and the energy being captured is increased. Seems like a win-win to me, if it were possible.

Solar-panel covered shuttering could do that.

Well blinds would presumably block the light you want in (visual spectrum). Furthermore, anything that isn't reflected back out serves to heat the building. Absorbing the energy in a PV material takes some fraction of energy that would otherwise become heat and turns it into something valuable.

Efficiency is very important but just one-big factor to consider in your application. Less efficient panels can have other benefits that justify their use. Crystalline silicon panels are more efficient than thin film but thin films are lighter and so can be used on roofs that don't support the heavier panels.

Blinds would block the light after the light has already passed through the solar panels. You get the shade plus the electricity.