Chemical bath deposition of PbS thin films on float glass substrates using a Pb(CH₃COO)₂-NaOH-(NH₂)₂CS- N(CH₂CH₂OH)₃-CH₃CH₂OH definite aqueous system and their structural, optical, and electrical/ photoelectrical characterization

Lead-sulfide thin films were synthesized at room temperature on float glass substrates by chemical bath deposition using a Pb(CH₃COO) ₂-NaOH-(NH₂)₂CS-N(CH₂CH ₂OH)₃-CH₃CH₂OH definite aqueous system. Although they were analyzed to determine their structural and optical characteristics, this work is focused on determining and discussing the electrical/photoelectrical properties of lead-sulfide thin films, due to the lack of publications centered on the correlation of these properties with deposition parameters. It is observed that an increase in immersion time during the deposition regime leads to an increase in the thin film thickness and crystallite size, and the latter, in turn, results in a decrease in the energy band gap. The evolution of the values of electrical/photoelectrical parameters with increasing immersion time is explained in terms of the prevalence of either the effect of increasing thin film thickness and crystallite size or the effect of increasing oxidation products. It is demonstrated that by depositing thin films during different immersion times within the first 24 h of reaction, nanocrystalline and photosensitive lead-sulfide thin films can be obtained with a thickness of up to approximately 296 nm, showing p-type conductivity and associated with the cubic crystalline structure (galena). Besides, a wide interval of optical and electrical/photoelectrical parameters values can be obtained, which can be chosen according to the desired application. It is suggested that the lead-sulfide thin film deposited during 4 h of reaction is suitable for incorporation in photovoltaic structures. It presents a thickness of 181 nm, a crystallite size of 13.8 nm, an energy band gap equal to 0.93 eV, a dark-conductivity of 0.158 S/cm, a light-conductivity of 0.307 S/cm, a photoconductivity of 0.149 S/cm, and a relative photosensitivity factor equal to 0.940.