how to make an working model of solar cell it is a project for students in school?

A working model of a solar cell would be a solar cell.
Unless the extremely low-powered copper oxide cell is what you want, you don't make them, you buy them (unless you happen to be a solar cell manufacturer, in which case you wouldn't be asking the question).
You can configure them, connect them, implement them, repair them, combine them or carry them off to old Virginny, but you don't make them without millions of dollars worth of specialized equipment.
Green plants can make their own solar "cells", in a sense.  Heck,  they make it look easy!
True, but try charging your iPod off of one of those....