The rear is printed in two parts. A thick layer of aluminium paste covers most of the cell and provides a back surface field (BSF). Silver strips are also printed on the cell for later soldering to the interconnect metal tabs.
After the front print is complete the cells are flipped over to print on the rear.
Printing the aluminium paste on the rear. The cell is just visible through the screen as it moves through the line. The aluminium printing is an expensive step since it is very thick and covers almost the whole cell.
A cell immediately after printing. Small gaps are left in the aluminium to print silver strips later in the process. Note how wet the paste is.
Drying the aluminium paste. Careful handling is essential since aluminium is a p-type dopant and any paste smudges that get on the front of the cell will shunt the cell completely.