A uniform ultrathin (<30 nm) CdS buffer layer was deposited by CBD by utilizing an alternative bath based on N-methylthiourea and was compared with the standard sulfur source. The CdS deposited by this new bath formulation was deposited separately on soda lime glass (SLG), sputtered molybdenum/ glass and co-evaporated copper indium gallium di-selenide (CIGS)/Mo/glass substrates. The CdS film properties were investigated by scanning electric microscope (SEM), X-ray diffraction (XRD), X-ray photoelectric spectroscopy (XPS), UV-vis spectroscopy, and quantum efficiency (QE). The films deposited with N-methylthiourea were found to have a similar granular structure, deposit in the same stoichiometry, and have similar device performance as the standard when deposited in the 60-80 nm film thickness range. When the CdS layer was deposited ultrathin in the 20-30 nm range, it was found to have good surface coverage with no evidence pinholes or device shunting. QE data indicated 40 nm thick CdS samples deposited using Thiourea as a sulfur source demonstrated better overall results however depositing a 20 nm thick CdS demonstrated N-methylthiourea as a sulfur source could deposit with good quantum efficiency and more consistently. Devices fabricated with ultrathin CdS using N-metyhlthiourea showed better device performance compared with devices fabricated using the standard CdS chemistry. (C) 2014 Elsevier B.V. All rights reserved.