This research investigates the transport and thermoelectric behaviors of the CZTSSe thin films. Both p-type and n-type films were successfully synthesized, allowing us to comprehensively study the characteristics of the full-composition CZTS. Cu contents in CZTS precursors were controlled from Cu/Zn + Sn = 0.7 to 0.9 with a constant Zn/Sn = 1. After salinization, the Cu/Zn + Sn ratio in CZTS thin films shows positive deviation from the precursor, ranging from 0.78 to 1.1 that indicated a Zn or Sn loss with the increase of Cu contents. A decline of Zn/Sn ratio in the films from 1.53 to 1.2 was obtained when Cu/Zn + Sn in precursors increased from 0.7 to 0.9, indicating a Zn loss. Hall measurement showed that the increase of Cu contents yielded an increase in the conductivity and carrier concentration. Conducting type of the CZTS changed from p-type to n-type when the Cu/Zn + Sn exceeded 1. Absorption spectroscopy revealed a decrease of band gap of CZTS and Raman spectroscopy indicated an increase in the full width at half maximum when the Cu content was increased. Photoluminescence spectroscopy analyses indicated a defect related peak with 47 meV lower than the band gap. Accordingly, CuZn + SnZn was proposed to be the dominated defects of the Cu-rich n-type CZTS thin films, different from the CuZn dominated p-type films. As a result, we proposed that the n-type CZTS with Cu/Zn + Sñ1.01 and Zn/Sñ1.1 CZTS had the best power factor than other composition. The result could be reference for CZTS thermoelectric research in the future.
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