SUNYIMA 100pcs Mini Solar Cells 0.5V 0.4W Micro Thin Polycrystalline Silicon Solar Panels DIY 52 x 52mm/2x2inch

Both sides produce a voltage in sunlight. They are rated at half-volt. I got about 0.3 volts with indoor shop light and about 0.6 volts in direct sunlight--see 10 sec video. They are fragile, I broke one right away. All solar cells are fragile, and the product description makes it clear they are fragile so that's fair. I had some trouble (maybe my own lack of skill) with soldering tabs, so I tried using clear wrapping tape and it made a good connection and much easier. The picture shows tabbing wire taped on to the cell, producing 5 to 6 volts charging a battery using the 5v micro USB charging port.

But with the title in mind, you SHOULD be discouraged if you are not well practiced and well equipped.I got .6 volts and 100mA on a Spring day, well past noon, in Maine, and it was my first try so there's actually a giant crack down the middle of the thing. With all that in mind, I bet it COULD generate the advertised .4 watts if soldered perfectly, undamaged and in equatorial sunlight in summer at noon.That's the absolute max, not the average in real-life scenarios.Furthermore, I suspect others do not realize this, but when soldering solar panels, you can't use cheap (poorly regulated) soldering irons, nor can you use the wrong type of solder.You must maintain a precise temperature, and your solder tip must be a perfectly flat surface held at a perfectly parallel angle to the strip.Finally, the strips you can find available on line are both too thick and too wide. For mine to work, I had to hammer strips to about half their thickness and then cut them to about 1.5-2mm width. It's a lot of work.

Pulled 5 cells at random from the stack all 5 held up under extreme conditions in a vacuum chamber failures began in hour 3 with no containment for the cell and hour 160 when they were housed in our panel array. To clarify in the vacuum chamber temperature was raised by 250° per hour so the unprotected cell melted somewhere around 650° which is very good the other 2 brands we tested melted between 450° and 550° all of which are well above where we need them to be able to survive 240° or so.

My husband bought these and even though he has a degree in electronics engineering and decades of experience he could not not get them to solder. He tried multiple solders, flux and soldering irons. Returned. They are junk!

Broken piece's toss in the trash. Handle with care. Good stuff, be careful, thin, and cracks easy.