The impact of chlorine (Cl) concentration in the chemical bath deposition (CBD) solution on the properties of post-deposition annealed cadmium sulfide (CdS) thin films on glass substrates was investigated. CBD CdS films with a thickness of 250 nm were deposited from a standard bath containing cadmium sulfate, ammonia and thiourea. For doping of the CdS films with Cl, ammonium chloride was also added to the bath. The CBD process is characterized by the opportunity it provides to incorporate solution components like hydroxide group and chlorine into the lattice of growing films. CBD CdS thin films with different [Cl]/[Cd] ratios were characterized. The structural as well as electrical and photoluminescence (PL) properties of CBD CdS thin films indicated the creation of electrically and optically active defects in the CdS lattice in the deposition process. Both the incorporated hydroxychloride groups and H-2 annealing play a substantial role in controlling the CdS electrical and optical properties. A good correlation between the PL and electrical properties of CBD CdS thin films was achieved and explained on the basis of a classical understanding of donor- acceptor pairs formed by the Cl-S(+) and (VCdClS)-centers and emergence of Cd excess in CBD CdS lattice due to destruction of incorporated hydroxide groups in the annealing process. (C) 2012 Elsevier B.V. All rights reserved.