CdSe films have been prepared successfully by an ultrasonic chemical bath method, with CdCl2·2.5H2O and Na2SeSO3 as precursors, and trisodium citrate as complexing agent. The films were characterized by XRD, AFM, and UV-Vis. The results showed that the CdSe films were n-type semiconductor and had absorption in the visible region. The CdSe film electrode had higher electron transfer rate, which leads to a substantial improvement on the photocurrent. Optimal
condition for preparing the CdSe thin films were as following: the ratio of Cd2+ to trisodium citrate was 1:1.5, the ratio of Cd2+ to Se2- was 2.5:1, the pH value was 10, the deposition time was 2.5h, and the annealing temperature was 350℃.