I thik you may be thinking this system provides light at night. Not so.
There is no formula. The bottle simply transfers sunlight into dark areas, the water within helping to conduct the light falling on the exposed top of the bottle. The light is refracted through the water, and exits within the dwelling.
The bleach is to prevent the water going green. The bottle is sealed tight to prevent loss of water and bleach, and to resist the pressure from heating by the sun.
Very simple and clever "technology"!
