Its estimated that a PV panel is co2 neutral aver 2 years.

And the great thing is: this is only if the panel was produced with fossil fuels. So due to increase in green energy everywere, this number goes down too and a PV can easily be used for 15 years and after. After that it might just be more economicly to reinvest in a new set of PV panels while the old ones can be sold and used somewere else.