inverted photocell (novice question)?
Usually you use a photocell


to measure light or 
to switch something on or off


For the latter, a normal photocell can be used for either purpose. If you want to switch something off or on  when light falls below a certain level or when light rises above a certain level.

You don't need a different sensor, just use it in a slightly different circuit.

Compare



LED lights when the LDR is dark &nbsp;&nbsp;&nbsp;&nbsp; LED lights when the LDR is bright
From Electronics Club / Transistor Circuits