In this study, a number of photoconductive photodetectors made from GaSe1-xSx (0≤x≤1) series layered semiconductors are presented, which are suitable for the detection of energies in the range of visible to ultraviolet (UV). Each photodetector consists of a gallium chalcogenide photoconductor and an electronic amplifier, forming an optical sensor unit covering the energy spectrum range from red (2 eV) to UV (∼5 eV). Spectral photoconductances of the GaSe1-xSx series layers with x=0, 0.1, 0.2, 0.3, 0.4, and 1 are characterized using photoconductivity measurements in the energy range of 2–4 eV, and the results of these measurements are analyzed. Photoluminescence and piezoreflectance measurements are carried out to identify the band-edge transitions of the layered GaSe1-xSx (0≤x≤1) compounds. From experimental analysis the transition origins of the band-edge transitions are clarified. The functional performance of three selective sensor units of GaSe, GaS, and two-color GaS/GaSe is tested using the spectral measurements of a xenon arc lamp. The emission line features from the xenon arc lamp are clearly resolved in the detection spectra of the sensor units. The results show a good functional performance of these layer compound photodetectors.