I get this question maybe once a week, usually from a new buyer who read something online. Monocrystalline or polycrystalline solar panel, which is better. The honest answer is it depends what the light costs.
Monocrystalline panels are cut from a single silicon crystal, so they're more efficient per square centimeter. On a small flashlight where the panel might only be 40 by 25 millimeters, that efficiency matters a lot, because you simply don't have room for a big panel. Every extra percent of conversion buys you real charging time.
So on our better models, the ones we sell to buyers who care about all-day reliability, we use mono. They cost more and they charge a dead 2000mAh cell back up in a sunny afternoon, more or less.
Poly panels are blue and a little speckled looking, cheaper to make, slightly less efficient. On a 2 dollar promotional torch where nobody expects miracles, poly is fine. The buyer wants a low price and a panel that does something, not a panel that does everything.
Where I push back is when someone wants a mono panel printed on the spec sheet but a poly price. That's where we lose money or you lose quality, one of the two. I'd rather just tell you which one your budget actually buys.
One thing people forget, by the way, is that the cheap clear epoxy coating yellows in strong UV after a year or so, and a yellowed coating drops output no matter which silicon is under it. We switched to a better laminate in 2022. That probably mattered more than the mono-versus-poly argument ever did.
