Photoelectricity of β-Agl under sub-bandgap illumination

An experimental study of the spectral, intensity and temperature dependences of the photoconductivity and contact photovoltage of β-AgI single crystals under sub-bandgap illumination is carried out. Both dc and ac photoconductivity experiments are performed and dark-to-light relaxation characteristics of the contact photovoltage are investigated. It is found that the processes under consideration are of a unified character in the spectral region below 2.20 eV, in which the photoconductivity spectrum follows Urbach's rule, temperature behaviour is opposite to that of dark conductivity and dependence on exciting light intensity is linear. A simple model is proposed to explain qualitatively the results obtained, based on the assumption for photoexcited ionic-type conductivity.