To reduce manufacturing cost for solar cells, we are trying to prepare a compound semiconductor ZnS(Te)Se and ZnCdS from solutions. The advantage of deposition from solutions is low cost. ZnS(Te)Se and ZnCdS is very suitable for window layers of heterojunction solar cells. At present, there are two popular deposition techniques from solutions, that is, chemical bath deposition (CBD) and electrochemical deposition (ECD). ECD has been investigated very extensively for variety of materials but not for ZnS(Te)Se. Moreover, the substrates must be conductive in ECD. On the other hand, the deposition of ZnS(Te)Se and ZnCdS by CBD have been reported by several research groups, and successfully used for fabrication of Al\p-CdS\ZnSSe and Al\p-CdS\ZnSeTe solar cells. Photochemical deposition (PCD) is a technique of film preparation from solutions by UV light illumination. In this study, ZnS(Te)Se thin films were deposited by PCD from an aqueous solution containing ZnSO4, TeO2 and Na2SSeO3. ZnCdS thin films were deposited by PCD from an aqueous solution containing ZnSO4, CdCl2 and Na2S2O3. In an acidic region (pH = 6.5) smooth films were prepared and the solution was stable. The films deposited from the solution were not transparent because the films contained crystalline Zn and Cd. This is because nucleation of crystalline Zn was suppressed by complex formation. As noted below, effects of complexing agents are also examined. pH was adjusted using H2SO4. An indium-tin-oxide (ITO)-coated glass sheet was used as the substrate. A degreased sheet was immersed at 3mm below the solution surface and illuminated by a high-pressure mercury lamp of 500W through a spherical simple lens. A diameter of the illuminated region was about 1cm. The growth solution was stirred constantly during the deposition. The temperature of the growth solutions was room temperature before the illumination, and it was increased slightly during the illumination, but did not exceed 60°C. The transmission of the film was much increased. The crystalline structure and quality was investigated by X-ray diffraction experiments. Crystalline quality as a function of the layer thickness was studied using an analysis of the integrated intensity of the X-ray diffraction peaks. Our investigation on both the physical properties of the ZnS(Te)Se and ZnCdS layers correlated to their thicknesses and on the growth mechanisms, allow us to propose an optimized photo, electrochemical bath deposition process of ZnS(Te)Se and ZnCdS . The absorption edge due to ZnSeTe was observed near 450-600 nm, but this absorption edge is not very sharp. This will be due to amorphous nature described above. The bandgap of the films ZnS(Te)Se deposited for 1h (3.2eV) and 2h (3.0eV) were in good agreement with the literature value(3-3.2 eV). The transmission of the films decreased with increasing deposition period. Thus, deposition longer than 2h seems to be detrimental to film properties and thickness. The morphological analysis was done using an optical microscope. Four point Probe was used for the measurement of the electrical resistivity of the films. X-ray diffraction (XRD) analysis was carried out, using a diffractometer for the ranging from 20° to 60° with CuK_(1.5418 Å) radiation. Surface morphology was investigated using an atomic force microscopy technique. The data obtained from the films was used to investigate the band gap energy and transition type of the thin films. The optical properties of films were studied by absorption measurements. The absorbance spectrum for the films deposited at pH 4 was recorded in the wavelength of 300-800 nm. This spectrum reveals that the films have low absorbance in the near infrared region while absorbance is high in the ultraviolet region. These films indicate a gradually increasing absorbance throughout the visible region, which makes it possible for this material to be used in a photoelectrochemical cell.