Chemical bath deposition (CBD) is a fairly simple synthetic route to prepare II-VI
semicondutive zinc sulfide thin films, which can be prepared on the flat surface of glass or silicon
wafer substrates in the solution containing the precursors of zinc and sulfur ions in terms of ambient
conditions of varying acidity. This study particularly aims at the growth dependence and optical
property of ZnS thin films in the CBD process by different experiment parameters, whereas we
intend to choose suitable types of zinc ionic precursors to be coupled with various CBD parameters
such as reaction temperature and time, precursor concentration, types and complexing agents as
well as post-deposition heat treatment conditions. Addition of different concentration of
ethylenediamine, ammonium sulfate, sodium citrate and hydrazine in the CBD reaction process was
used to control the adequate growth rate of ZnS thin films. As a consequence, the rapid thermal
annealing was employed to enhance the film uniformity and thickness evenness, transmittance and
the energy gap of ZnS samples. The results would lead to a potential application of buffer layer for
the Cu (In,Ga)Se2 based thin film solar cells. The analytic instrument including SEM, AFM,
UV-VIS were used to examine the CBD-derived nanosized ZnS buffer layers for the thin film solar
cells. The ZnS thin films prepared by the chemical bath deposition in this study results in film
thickness of 80 ~ 100 nm, high transmittance of 80~85% and the energy gap of 3.89 ~ 3.98 eV.
Optical and Structural Characterization of Cd-Free Buffer Layers Fabricated by Chemical Bath Deposition