I’m not touching any civ game until it got it’s two DLCs. 5 and 6 had only a really good game loop after them and it’s cheaper that way. I’m not alone in this I think which might be half of the reason for the struggle.

With one layer the case is simple. There is a certain light energy at which the conversion of light to current occurs called gap energy. If the light energy is lower than that no conversion can happen and if the light energy is higher the extra energy is converted to heat and only gap energy remains.

Filtering UV would be a loss but a small one.