Due expensive nature of silicon solar cells with indirect energy band gap, low-cost fabricated chalcogenide thin films are in focus. Copper aluminium diselenide (CuAlSe₂) compound thin films are prepared by chemical bath deposition (CBD) technique. The films were deposited onto microscope glass slide (7.5 cm x 2.5 cm x 0.1 cm) in which influence of ammonium solution as pH adjuster is studied. The optical properties of deposited films were studied using UV-Vis spectrophotometer and results showed that the films thicknesses decrease as the volume ammonium solution increase which resulted in hindering films deposition an as well affected the energy band gaps (2.3 eV to 3.0 eV) of the deposited films as pH values decrease. The pH played important role during the deposition process by affecting the optical properties of the films. This material is good candidate for optoelectronic properties by having moderate transmission in visible region of the spectrum and good UV filter since it absorbs higher in ultraviolet region.

Keywords: Thin Films; Optical Properties; Copper Aluminum Diselenide; Ammonium Solution;