Khemraj,

Most common flat-plate PV panels have a thick positively doped layer with a thin (only a few microns) negatively doped "top" layer.

The negatively doped side receives the irradiance, so that excited electrons enter the positive side, and the plate acts as a source accordingly.

The bulk side being positive, is encased and grounded. Consequently, in most cases you will encounter a grounded positive side.

-Sanjay