what is this ? light sensor from projection TV

I was able to get a couple of these from a projection TV. they were located on the inside of the front glass and there was one on each side.

I believe that these could be some from of light resistive sensor. only 2 wires connected, and a SMT chip, silk screen indicates a diode. letters are C2.

any ideas ?

I light-sensing diode would be a photodiode.

According to the service manual for the projector it comes from its a solar battery.