What happens in PS-II?

Photolysis of water happens in PS-II.
Photosystem II is the first protein complex in the light-dependent reactions of oxygenic photosynthesis.
Within the photosystem, enzymes capture photons of light to energize electrons, and these energized electrons are replaced by oxidizing water to form hydrogen ions and molecular oxygen. That is photolysis means the breakdown of water in the presence of light.