The study of the pseudobinary system Cu2SnS3-Cu2SiS3 shows that a solid solution (Cu2SixSn1-xS3) exists in the range 0.4 <= Si/(Sn+Si) <= 0.6. Based on diffuse reflectance and photoelectrochemical measurements these compounds show potential as absorber materials for photovoltaic devices. The compounds were prepared at 850 degrees C from copper sulfide, silicon, tin, and sulfur and were analyzed with single-crystal (for x approximate to 0.40) and powder diffraction techniques. Optical band gaps of 1.25, 1.35, and 1.45 eV were observed for the three compositions x = 0.39, 0.48, and 0.61; cathodic photocurrent occurring is significant.