Reddit mentions of Solid State Physics

Sure!

The Physics of Solar Cells by Jenny Nelson is a nice book. Very dense, a little mathy, and assumes some prior knowledege.

This book by Martin Green is the gold standard, though it is probably less accessible than Nelson's and harder to find.

It's probably necessary to have a good grasp of freshman physics, and it would certainly be helpful to understand classical electrodynamics and some solid state physics, which itself requires a little bit of quantum mechanics.

Necessary math for all of this is some calculus, some differential equations, and some linear algebra.

There may be a much friendlier resource out there; I understand if this is a formidable stack.