Polycrystalline silicon solar cells are cheaper than monocrystalline and have lower efficiency but are better if sun rays are not perpendicular. The surface of cells shows various tones of blue due to orientation of silicon crystals.
<a href="//commons.wikimedia.org/wiki/User:Mariojan_photo" title="User:Mariojan photo">Mariojan photo</a>
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<span class="int-own-work" lang="en">Own work</span>