[pjc50]

Ah, the good old "I know nothing about this but assume it must be easy"!

It's materials processing. They're only "basically sand" in the sense that glass or microchips are. The key step is purification of silicon, which is like distillation in the liquid/solid phase. It's very energy-intensive. This then gives you a solid cylinder of pure silicon.

To make cells, you slice this like a ham. Except it's extremely hard, so you need a diamond saw: http://www.asahidia.co.jp/eng/wp-content/uploads/2015/05/B51... and, like sawing wood, the material from the cut ("kerf") is wasted.

A surprising amount of recent cost reductions have been due to making the cells thinner and making the cut as thin and clean as possible.

They are then run through some annoyingly toxic chemical processes, given an antireflective coating, have silver wiring attached, and packaged into a glass or polycarbonate fronted housing.

[rsfern]

And the alternative technologies -- e.g. vapor deposition processes for thin film photovoltaics -- aren't exactly cheap either.