How Photoresistor Works

§   Special semiconductor crystal, such as cadmium sulfide or leaD sulfide is used to make photoresistors.

• § When this semiconductor is placed in dark, electrons within its structure resist flow through the resistor because they are too strongly bound to the crystal’s atoms.

• § When this semiconductor is illuminated, incoming photons of light collide with the bound

electrons, stripping them from the binding atom, thus creating holes in the process.

• § Liberated electrons contribute to the current flowing through the device.