I'm not sure which of two things you mean [EDIT: perhaps both], but neither of them seems to make sense.
1. "All those LCDs and TVs won't need to be backlit; they'll just use whatever light there was behind them." By definition, if you do that then they can't be brighter than whatever was behind them; and unless what's behind them is nice and uniform, you won't be able to see them clearly. This just isn't going to look good enough for the purposes most of those displays are there for.
2. "We'll power the LCDs and TVs photoelectrically, using the ambient light." Then you'll need a large area of photovoltaic cells to power them, somewhere that was well-illuminated but black. You could save more electricity by painting that area white instead and reducing the lighting slightly.
1. "All those LCDs and TVs won't need to be backlit; they'll just use whatever light there was behind them." By definition, if you do that then they can't be brighter than whatever was behind them; and unless what's behind them is nice and uniform, you won't be able to see them clearly. This just isn't going to look good enough for the purposes most of those displays are there for.
2. "We'll power the LCDs and TVs photoelectrically, using the ambient light." Then you'll need a large area of photovoltaic cells to power them, somewhere that was well-illuminated but black. You could save more electricity by painting that area white instead and reducing the lighting slightly.