Achieving highly efficient kesterite solar cells using simultaneous surface Ge substitution and rear interface engineering strategies

Facile Approach for Metallic Precursor Engineering for Efficient Kesterite Thin-Film Solar Cells

“…Raman spectroscopy was employed to carefully understand antisite defects and defect clusters of CZTSSe and ACZTSSe thin films, as shown in Figure h. The vibrational modes of Raman analysis were used to determine the defect concentration of the absorber layer, where the strong Raman peak at 198 cm –1 corresponds to the kesterite phase, and the two weak peaks at 171 and 233 cm –1 are associated with the A-type [Zn Cu + V cu ], B-type [2Zn Cu + Zn Sn ], and C-type [2Cu Zn + Sn Zn ] defect clusters . In “ACZTSSe” thin films, the strong Raman peak position is shifted from 198 to 203 cm –1 , indicating the successful Ag elements into the kesterite crystal lattice .…”

“…In “ACZTSSe” thin films, the strong Raman peak position is shifted from 198 to 203 cm –1 , indicating the successful Ag elements into the kesterite crystal lattice . Commonly, the Cu-poor and Zn-rich composition in kesterite can promote the formation of antisite defects (i.e., Cu Zn and Zn Cu ) and related defect clusters (i.e., A-, B-, and C-types) owing to their relatively low formation energy. , The peak at 171 cm –1 corresponds to V Cu and Zn Cu antisite defects and their related A-type [Zn Cu + V Cu ] defect clusters, while the peak at 233 cm –1 corresponds to Cu Zn antisite defects and their related B- and C-type defect clusters owing to Cu/Zn and Cu/Sn atomic plane vibrations . Significant changes in the intensity of the two weak peaks are observed in ACZTSSe compared with that of CZTSSe.…”

“…The decreased G sh indicates improved absorber crystal quality due to the reduced antisite defect density and related defect clusters and that cause recombination in the bulk. 36 The R s values for CZTSSe and ACZTSSe TFSCs using "S-Ag" and "E-Ag" are estimated to be 4.43, 2.10, and 3.32 Ωcm 2 , respectively, as shown in Figure 6c. The reduced R s value in ACZTSSe TFSCs compared to CZTSSe significantly contributes to the improvement of the FF value.…”

“…The deposition of baseline metallic stack layers was carried out using Cu (99.99%), Sn (99.99%), and Zn (99.99%) targets with a power density of 0.658, 0.658, and 0.439 W/cm 2 , respectively. Each thicknesses of Cu, Zn, and Sn are approximately 177, 221, and 212 nm, respectively. , Following that, an alloying process was conducted for 1 h at 280 °C in a tube-type furnace to form Cu–Zn and Cu–Sn alloys, which inhibited Sn loss and promoted a favorable formation pathway for CZTSSe during the synthesis process (see Figure S3). − In this study, we conducted precursor engineering by introducing a 4 nm-thick Ag layer at four different positions within a stacked metallic precursor, using either evaporation or sputtering techniques, before the alloying process.…”

“…27 The dark I−V curve was performed to assess the quality of the bulk and absorber/buffer interfaces. 36 We have listed the dark I−V parameters such as diode ideal factor (n), series resistance (R s ), shunt conductance (G sh ), and reverse saturation current (J 0 ) as shown in Figures 6c,d and S10 and Table S3. As shown in Figure S10b, the J 0 values of CZTSSe and ACZTSSe TFSCs using "S-Ag" and "E-Ag" were 0.0365, 0.0371, and 0.0761 mA/cm 2 , respectively.…”