"1954 – The first practical photovoltaic cell was publicly demonstrated at Bell Laboratories.[27] The inventors were Calvin Souther Fuller, Daryl Chapin and Gerald Pearson.[28]"

The references are on Wikipedia. Maybe do the most basic thing in Wikipedia and click on some links to the related pages before asking for sources. One can still quibble that 'first practical' is indeed different from 'first' but the practical part is the part that actually matters in this argument anyway (i.e. solar rollout).

(also, of course it was Bell Labs.)

Haha my exact reaction when I first found out.