Photoelectrochemical Behavior of Bi₂S₃ Nanoclusters and Nanostructured Thin Films

Quantized semiconductor nanoclusters of Bi 2 S 3 are prepared in acetonitrile by reacting BiI 3 with H 2 S or Na 2 S. Both preparation methods yield stable colloids with particle diameters of ≤5 nm. Excitation with a 355-nm laser pulse results in transient bleaching in the 400−500-nm region. This process is followed by the formation of S - surf with a difference absorption maximum around 540 nm. This we attribute to the chemical changes associated with the hole-trapping process. A composite thin film electrode comprised of SnO 2 /Bi 2 S 3 nanocrystallites has been prepared by sequential deposition of SnO 2 and Bi 2 S 3 films onto an optically transparent electrode, and its photoelectrochemical behavior has been studied. The thin film is photoactive in the visible and near-IR and exhibits an incident photon to photocurrent efficiency (IPCE) of ∼15% at 400 nm.