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Cd_1–xZn_xS (CdZnS) is a promising replacement for the CdS buffer layers in copper indium gallium (di)selenide (CIGS) solar cells because the wider band gap of CdZnS offers improved optical transmittance of blue light. Chemical bath deposition (CBD) is the state-of-the-art deposition method for CdS and CdZnS. However, CBD of CdZnS is poorly understood, and relationships between bath composition and stoichiometry, microstructure, and optoelectronic properties of the deposited film are lacking. We introduce CBD using a continuous flow microreactor as a new technique to rapidly explore a wide variety of deposition conditions on a single substrate using spatially dependent characterization. X-ray diffraction and X-ray absorption spectroscopy indicate that the film is a mixture of nanocrystalline CdZnS and amorphous Zn(O,OH,S). Over the length of a single substrate, films showed increasing Zn:Cd ratio in the …