I think the most basic answer is no, more deeper answer would be not in the Christian way. Even from the Chronica Slavorum you can see that said Slavs didn't treat him in the way Christians treat the Devil. There are no sacrifices/prayers for the Devil in Christianity. With the premise that he's not just a Helmond's made-up god, there's in my option very good theory about him being the same as the god Veles, one of creation gods where the white one is connected with life and sky/light while the black one is connected with the death and underworld/darkness (this is a concept known to many mythologies around the world). Which of course is making the black god (cerno bog) more connected to the "bad things" in human eyes for death and all the underworld demons etc. are more dangerous to/hated by the living than is for example the sun. Yet they knew that it's exactly this god who could help them to control the dangerous beings and so he was good to them, too - in the way of all gods who are commonly capable of both, awesome and terrible things.
In old slavic stories that survived till today, you can commonly read about a "dark lord" etc. who is under the Christian influence basically understood as the Devil and is usually offering or protecting gold, magic or taking human souls etc. And people are commonly using the black color instead of an actual name which could be dangerous to say (even more after Christianity arrived) so it's likely that Cernobog was a similar thing - a secondary name created from the basic descriptors.
There's actually a god known from Rujána/Rügen who could be also connected and is not mentioned by Helmond only. it's Cernoglav (Tiarnaglofi, black-headed) whose temple was on Jasmund. He's mentioned in the Knýtlinga saga.
EDIT: Just as an interesting addition, Triglav (e.g. in Štětín/Szczecin/Stettin...) is also connected to the "dark side" as his oracle horse was black (in contrary to the white horse of Svarožič and Svantovít).