Thermally evaporated thin films of Sn10Sb20 − xBixSe70 (0 ≤ x ≤ 4) chalcogenide system were subjected to X-ray diffraction studies to check the amorphous nature of all the films. The dark conductivity increases with the increase in Bi content and the calculated values of dc activation energy initially increase for smaller Bi concentration and then decrease sharply with further addition of Bi. The photocurrent in the beginning 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 slow decay. Photocurrent versus light intensity follows the power law Iph ∝ Fγ and the values of exponent are also discussed. Except for x = 4 composition the photosensitivity drops for all the samples as the percentage of Bi increases. The values of differential lifetime determined from the decay curves are also reported.