hope you all are well
The bypass diode is usually connected in parallel with PV cell to avoid hot spot and prevent more PV output power losses. The bypass diode is connected in opposite direction to the PV cells in such way that it conduct when the PV cell is shaded by (tree).
My question is that what prevent the DC current generated by a string of PV cells in a normal condition ( no shading) from passing through the bypass diode and not through PV cell ? and why the current can flow through the bypass diode only in the shaded PV cell.