Cu(In,Ga)Se2 (CIGSe) thin-film solar cells are a commercial photovoltaic technology that provides sustainable power. Here, we study the formation of Zn1-xSnxOy (ZTO) thin films as Cd-free buffer layers by chemical bath deposition (CBD) suitable for CIGSe solar cell devices. ZTO films were obtained by CBD onto SLG, by modifying a reported procedure otherwise leading to columnar ZnO thin films. Our ZTO films show a flatter morphology compared to the reference ZnO due to inhibition of the columnar growth. In addition, a non-trivial increase of the band gap was observed by enhancing Sn concentration. When a concentration of 20% [Sn]/([Sn]+[Zn]) (where [Sn] and [Zn] are the molar concentrations of Sn and Zn, respectively) is employed in the chemical bath, the resulting buffer layer allowed the CIGSe solar cell to achieve similar performance as with a CdS buffer layer (average efficiency of (11 ± 2)% ), yielding a maximum efficiency of 10.4%, with an average of (9 ± 2) %.