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 (I-ph) versus light intensity (F) follows the power law I-ph proportional to F-gamma and the value of the exponent (gamma) 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. (C) 2009 Elsevier B.V. All rights reserved.