Enhancement of power conversion efficiency of Ag-substituted Cu2ZnSn(S,Se)4 solar cells via tuning Cu2+/(Cu++Cu2+) percentage in precursor solution

• Published in: Solar energy materials and solar cells Vol. 261; p. 112502
• Main Authors: Zhang, Jiayong, Yao, Bin, Ding, Zhanhui, Li, Yongfeng, Ma, Ding, Li, Mengge, Sun, Yuting, Wang, Chunkai, Liu, Yue, Sun, Xiaofei
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.10.2023
• Subjects: Ag-substituted; Copper salt; Depletion layer width; Kesterite solar cells; Kesterite solar cells; Copper salt; Ag-substituted; Depletion layer width
• DOI: 10.1016/j.solmat.2023.112502
• ISSN: 0927-0248

Although trace silver (Ag) substitution for Cu in Cu2ZnSn(S, Se)4 (CZTSSe) offers benefits in improving open-circuit voltage (VOC) of CZTSSe solar cells, its further development is still hindered by the fairly low short-circuit current density (JSC) owing to the increase of bandgap (Eg) of the absorber layer. Herein, a strategy is demonstrated to mitigate the poor JSC arising from the Ag substitution by tuning the Cu2+/(Cu++Cu2+) percentage in the (Cu, Ag)2ZnSnS4 (CAZTS) precursor solution. Depth characterization indicates that the appropriate Cu2+/(Cu++Cu2+) percentage in the CAZTS precursor solution increases the photogenerated charges separation and carrier transport processes for Ag-substituted CZTSSe (CAZTSSe) solar cells. Benefiting from this strategy, the power conversion efficiency (PCE) of 9.57% is achieved when the Cu2+/(Cu++Cu2+) is 50 at.%. The main factor for the improvement of PCE is due to the increase in photogenerated current density (JL) and decrease in shunt resistance (Rsh). It is demonstrated that the increase in JL results from a widening in the depletion layer width (Wd) of the p-n junction and an increase in carrier lifetime, induced by optimization of the Cu2+/(Cu++Cu2+) percentage. While the decrease in Rsh comes from the change of reaction pathways due to the change in Cu2+/(Cu++Cu2+) percentage. The enhancement of power conversion efficiency (PCE) for Ag-substituted CZTSSe solar cells is achieved through adjust the Cu2+/(Cu++Cu2+) percentage in preparing CAZTS precursor solution, which is mainly induced by the increment of JSC. [Display omitted] •Experimental parameters for the fabrication of Ag-substituted Cu2ZnSn(S, Se)4 (CAZTSSe) solar cells were optimized.•The JSC of CAZTSSe solar cells can be adjusted by tuning the Cu2+/(Cu++Cu2+) in preparing the CAZTS precursor solution.•Best efficiency for CAZTSSe solar cell was achieved when the Cu2+/(Cu++Cu2+) in CAZTS precursor solution was 50 at.%.•Photogenerated charge separation and carrier transport for CAZTSSe solar cells can be increased, thus improving performance.