The photoelectrochemical behavior of synthetic crystals of WS 2, MoS 2 and crystals with mixed metal and chalcogen composition was studied and compared with the behavior of MoSe 2 and WSe 2. The composition and stoichiometry of the crystals and the composition of the electrolyte are varied and the behavior of the materials in a regenerative liquid junction solar cell is measured and analyzed. The quantum yields as a function of wavelength and photon flux are investigated and sunlight to electricity conversion efficiencies are measured. The formation of iodine layers on the photoelectrode surface under high illumination intensity was observed and discussed with respect to the use of these materials with solar concentrators.