Abstract: The photoelectric conversion efficiency is enhanced about 20% by using FeCl₃ solution to modify the n-CdTe photoanode. By the aid of X-ray photoelectron spectroscopy and Auger electron spectroscopy,the variations of chemical compositions and surface structures after FeCl₃ modification are detected. The photoelectrochemical and electrochemical behaviors of the modified electrodes are examined by the spectral response, capacitance-potential, and electrochemical impedance measurements. The Fermi level pinning at the n-CdTe/solution interface is observed. Furthermore, a preliminary explanation for the modification action of FeCl₃ is given.