Abstract: The present invention provides a Cu2ZnSnSe4 (CZTSe) nanoink composition and a CZTSe sputtering target thereof for use in manufacturing an absorption layer of a thin-film solar cell. The CZTSe sputtering target includes a binary multiphase mixture and/or a ternary multiphase mixture. The CZTSe nanoink composition not only includes the binary multiphase mixture and/or ternary multiphase mixture but also includes a chelating agent. Any two of Cu, Zn, Sn, and Se are combined by the chelating agent to form the binary multiphase mixture. Alternatively, any three of Cu, Zn, Sn, and Se are combined by the chelating agent to form the ternary multiphase mixture. By manufacturing the absorption layer of the thin-film solar cell in the aforesaid manner, the absorption layer has a perfect quaternary monophase structure but does not manifest any impure phase detrimental to photoelectric conversion efficiency.