How can I understand the working principles of solar cells?
Read as many books as you can.
All in all, the working principle of a solar cell can be understood in this way, a high technology that use the sun energy for electricity.
As a complicated science which is quite new, you will spend lot of time in the research and analysis of solar cells.
You have to spend more time than you thought to really understand it.
My way of understand the working principles of solar cells is to read tons of books about that topic.
