I see one solar cell available in Fritzing. This part is tagged as solarbit-12x1.
A generic data sheet seems to indicate that the negative lead would come out of the top of the cell, when it’s not coming out of the right side.
And of course, the data sheet images lack a notch, which I half remember goes on the left.
Could the part get some basic plus (+) and minus (-) symbols to clarify?
Could more parts include a PDF link to their data sheet?