Effect of isoelectronic substitution of Bi on the photoelectrical properties in amorphous Sn–Sb–Se films

Amorphous thin films of Sn10Sb20 − xBixSe70 (0 ≤ x ≤ 6) system have been prepared by thermal evaporation technique. The optical gap and dc activation energy first increases with the addition of Bi (x = 2) and then decreases sharply with further addition. The photocurrent initially increases with time and then saturates to a constant value for all the samples. The decay portion of photocurrent has two components, fast one followed by a slow decay. Photocurrent (Iph) versus light intensity (F) follows the power law Iph ∝ Fγ and the value of the exponent (γ) decreases from 0.76 to 0.53 as the Bi concentration varied from x = 0 to 6 in the present system. The photosensitivity of these samples varies from 1.27 to 1.13 as Bi content increases.