Influence of sulfurization time and Cu-ZnS-Sn stack order on the properties of thermally evaporated CZTS thin films

Abstract

Cu2ZnSnS4 (CZTS) thin films were synthesized in a two-step procedure. Sulfurization of stacked thin films SLG/ZnS/Sn/Cu (S1) and SLG/Cu/Sn/ZnS (S2) after sequential deposition of Cu, ZnS, and Sn precursors was carried out. At 550 °C, two sulfurization periods were applied to both stack orders. Sample S1 sulfurized for 30 min (S1-T30) had a better crystallite size of roughly 50 nm, lower lattice strain, and lower dislocation density than other samples. The Cu/Zn cation ordering in the CZTS crystal system was significantly affected by stack sequence and sulfurization time, according to Q-factor calculation. The stack order of the S1 series allowed for homogenous and distinct particle development. From the elemental analysis, it is observed that the stack sequence and sulfurization used for sample S1-T30 permitted a near stoichiometric composition. The sample S1-T30 exhibited an optimal band gap value of 1.47 eV. To propose feasible alterations in the structural ordering, band gap calculations were used. In comparison to the stack order of the S2 series, the stack order SLG/ZnS/Sn/Cu with a sulfurization time of 30 min created a single-phase CZTS, implying less synthesis time to obtain an absorber quality CZTS layer for solar photovoltaic application.

Recent Progress and Challenges in Controlling Secondary Phases in Kesterite CZT(S/Se) Thin Films: A Critical Review

“…The substrate may have controlled movement for uniform film deposition (Figure 4). The deposition of CZT(S/Se) films by evaporation can be achieved through two different approaches: single-step deposition [30,31], where all the precursors are simultaneously deposited and then followed by sulfurization, and sequential two-step deposition using different metallic or binary precursors, in different combinations and sequences, such as Cu/Sn/Zn/Cu, Cu/Sn/Cu/Zn [32], Cu-ZnS-Sn [33] or CuSn/Zn/Se/CuSn/Se [34], followed by annealing with a sulfur or selenium source.…”