Another problem with cellular photosynthesis is that about 50% of the primary energy obtained is used for cellular respiration. The advantage of silicon is it doesn't eat or breathe.
Note that there are triple-junction photovoltaic cells, which are build in layers each optimized to absorb a different wavelenght of light (addressing the band gap issue). Better performance and efficiency, but much more expensive. Typically only used in spacecraft, but not economical on Earth where you can just buy 3x the panels for 1/15th of the price.
Maybe I'm in the wrong forum...