Firstly, you may be wondering why you would want to split a solar cell into two? There are two primary reasons, one to boost voltage with a limited number of cells or area and the second is if you have broken cells and you wish to cut the broken side off and still make use of the undamaged side.
When you need to boost the voltage output of your homemade solar panel and you do not want to buy a voltage regulator, you could try splitting your solar cells into two. With two halves of a 0.5V cell, you can connect them in series and get a voltage output of 1V. All that happens is your power output from the original cell is divided in two as well, so you will be left with two 0.5V 2W cells from one original 0.5V 4W cell.
Solar cells are not damaged by cutting them in half. As long as you retain the full tabs on the front and back of the cell, the divided cells with still produce the full voltage. This means that a solar cell can only be divided along lines parallel to the tab lines and can only be divided by the number of tabs. For example, if you have a double tabbed cell, you can split it into two while if you have a triple tabbed cell, you can split it into three smaller cells.