How to cut solar cells

We have all seen miniature solar panels that supply all kinds of gadgets: pocket calculators, solar garden lights, fan caps, toys etc.. In all these cases, they prolong battery life, or even replace them altogether, all you need is just ... Light.

If the solar cells have long been just a dream because almost nonexistent supply and prohibitive price, lately photovoltaic cells price dropped sharply on the open market, and the now supply is abundant.

The most common photovoltaic cells, are those with dimensions 80x150mm (3x6 inch) with electrical characteristics 0.5V, 3.6Amp, 1.8W and those with dimensions 150x150mm (6x6 inch) with electrical characteristics 0.5V, 7.5A, 3.8W.

A solar panel is usually made by connecting in series (or sometimes series-parallel) of a number of photovoltaic cells. When connected in series, generated voltage will be equal to the sum of each cell voltage and current remains the same, when connected in parallel, the voltage remains the same but the total current is equal to the current generated by individual cells.

Usual in domestic installations using renewable energy to produce electricity (solar and wind), 12V or 24V lead acid battery are a standard, therefore a solar panel will contain a minimum of 36 cells necessary to load such a battery. A panel that uses 36 solar cells size 3x6 will generate 18V, 3.6Amp, 60W with an area of ​​0.5 m2 and the one who uses 6x6 cells will generate 18V, 7.5Amp, 130W with an area of ​​1 m2

These photovoltaic systems are life saviour for homes or vacation homes not connected to grid, but for a wide range of portable and low power applications they are not suited, especially because of size and weight of the finished panel.

In these situations, the simplest solution is to make a solar panel using solar cells smaller than the standard, which of course produce smaller current, proportional to surface, but at the same voltage 0.5V.

For example, a mini solar panel for a garden lamp (picture below), uses 8 mini-solar cells connected in series in order to load a package of two NiCd or NiMh batteries. Each cell generates 0.5V 50mA and panel consisting of the 8 cells connected in series will generate 0.5 x 8 = 4V 50mA

Thus, for a small solar panel, it is absolutely necessary to find a way to obtain solar cells smaller than the standard 3x6 or 6x6 solar cells. But this is easier to said ... much harder to do ...
Prior to succeed, because I have to tell you that I finally succeeded, I tried many methods and I had many sleepless nights...

  • I tried by scratching with a cutter or knife and then break - did not work at all, broke everywhere except where it should break...
  • I tried chemically by reaction with NaOH, one of the few common substances that react with silicon - if I had time until retirement maybe it would have worked in this way
  • with diamond cutting disc - I hadn't the necessary tools to try but it is possible to work in this way
  • diamond tipped glass cutter (not with cutting wheels) - EVRIKA!

From the very beginning when I tried to cut solar cells using the diamond glass cutter, I was successful.
However, there are a few details that will ensure a high success rate and fewer rejects:

  • almost certainly you will destroy most of the first cells, so be brave!
  • solar cells you are trying to cut should be as flat as possible, without any surface imperfections
  • use a diamond tipped glass cutter (not with cutting wheels), can be a cheap model (like mine) but it is essential to scratch glass (or cell) only with a gentle push
  • work on a very flat surface without any impurity (I use a sheet of glass)
  • use a ruler when making scratching, a perfectly straight metal one would be preferable
  • even if a cell is broken, does not mean it's useless ... can be cut into smaller pieces, the only condition being the existence of the anode and cathode. From this point of view it is much better to work with cells having on back side, bar type connections like those on the front side, thus you can reuse many "pieces" that would otherwise be thrown away

If you have met at least in part the above, eventually you will get up to 60 such small cells from a 6x6 inch cell, each of them able to generate 0.5V at a current of about 100mA

Finally, as proof, I made ​​a short film to illustrate the above.