Photoconductivity ensues when the material is bombarded with photons of sufficient energy to raise electrons across the band gap, a forbidden region between the valence and conduction bands. ... In lead sulfide the gap energy is 0.41 eV, making this material sensitive to infrared light.

What is the principle of photoconductivity?

Photoconductivity is an optical and electrical phenomenon in which a material becomes more electrically conductive due to the absorption of electromagnetic radiation such as visible light, ultraviolet light, infrared light, or gamma radiation.

What is photoconductivity in semiconductor?

Photoconductivity [44] Δσ is defined as the increase of conductivity occurring in a semiconductor under optical excitation. When light of near-band-gap energy hits a homogeneous semiconductor, conductivity increases by the amount Δσ due, in most cases, to the increase of the free carrier densities Δp and Δn: (31)