monocrystalline silicon solar charger will slightly more expensive?

Hello,

A power bank is urgently needed for me!! However, I am an environmentalist and i make an desicion to a solar charger instead of normal power bank. To my astonishment, it will cost me much higher to buy such item. Glib, I know, I've often said it myself to wind up environmentalists. But i think i can't afford it. Most of the dealers claim that their products are made using monocrystalline silicon in multiple rows of two stacked wafers of doped silicon, which make it cost more. I found one at (KE-505S)5000mah portable solar charger-5000mAh KE-505S-portable power bank£¬power bank charger£¬power bank manufacturer-SHENZHEN KOEOK ELECTRONICS TECHNOLOGY CO.,LTD , and they told me that monocrystalline silicon as the most efficient and well known type of solar panel is slightly more expensive, but has many additional features. And the point is, it will cost twice as much again as the same product on ebay. How can I discriminate them?

b&

Dude if you went with polycrystalline or even multicrystalline silicon you could still probably get just a little less than 21% efficiency.

There's no real reason to go with Mono-Si unless you can afford it. If you were a business with high power usage that needed multiple solar banks I might understand putting in the extra cash for a high grade material, but as it is, you're fine with the cheap stuff.