Efficiency enhancement of Cu2ZnSn(S, Se)4 solar cells by addition a CuSe intermediate layer between Cu2ZnSn(S, Se)4 and Mo electrode

A CuSe intermediate layer (IL) is prepared between CZTSSe and Mo electrode to decay the carrier recombination on the rear surface of the CZTSSe absorber. The power conversion efficiency (PCE) can be increased from 7.52% to 10.09% by optimizing the thickness of CuSe IL. The increased PCE comes from improvement in filling factor (FF), short-circuit current density (JSC), and open-circuit voltage (VOC), and their contribution percent is calculated to be 63.08%, 24.83%, and 12.09%, respectively. It is demonstrated that boosted FF is mainly due to decreased reverse saturation current density (J0), raised JSC owing to higher photogenerated current density (JL), and enhanced VOC caused by decreased J0 and higher JL. The contribution percent of (ideal factor (A), J0), JL, Rs, and shunt resistance (Rsh) to increased PCE is calculated to be 60.84%, 27.41%, 10.33%, and 1.42%, respectively. By experimental characterization and SCAPS-1D simulation, it is suggested that decreased J0 results from the formation of passivation field and high electron potential barrier at the rear surface of CZTSSe due to the addition of suitable thickness CuSe IL, higher JL from the increase in width of the depletion region of CZTSSe/CdS, lower Rs from decrease in thickness of Mo(S, Se)2, and bigger Rsh from improved crystal quality of CZTSSe absorber.