Solarex panels are made of polycrystalline silicon. These are close in efficiency but polycrystalline cells are easier to make because small crystals take less time to grow than big ones. Astropower PV panels are made of microcrystalline silicon, which again is easier to make. A very different type of cell is made of amorphous silicon, that is completely non-crystalline. Thus they are very cheap and lightweight.
Most solar calculators use amorphous cells.
A recent development by Solarex is the advent of double junction amorphous cells. So although most PV for powering houses and buildings is now crystalline, this might change in the next 2 or 3 years, because amorphous is so cheap to manufacture. There is one other type of PV which is common in the aerospace industry, gallium arsenide. They are still very expensive and used only on spacecraft. Because the solar cell is a solid state device, it can last for decades.