Novel Chemical Route for Deposition of Cu2ZnSnS4 Photovoltaic Absorbers

Abstract

This work reports results of a study carried out to optimize the preparation conditions of Cu 2 ZnSnS 4 (CZTS) thin films grown by sequential deposition of Cu 2 SnS 3 (CTS) and ZnS layers, where the Cu 2 SnS 3 compound was grown using a novel procedure consisting of simultaneous precipitation of Cu 2 S and SnS 2 performed by diffusion membrane assisted chemical bath deposition (CBD) technique. The precipitation across the diffusion membranes allows achieving moderate control of release of metal ions into the work solution favoring the heterogeneous growth mainly through an ion-ion mechanism. Through a parameters study, conditions were found to grow Cu 2 SnS 3 thin films which were used as precursors for the formation of Cu 2 ZnSnS 4 films. The formation of CZTS thin films grown in the Cu 2 ZnSnS 4 phase was verified through measurements of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Solar cells with efficiencies of 4.9% were obtained using CZTS films prepared by membrane assisted CBD technique as absorber layer.

A Two-Step Magnetron Sputtering Approach for the Synthesis of Cu2ZnSnS4 Films from Cu2SnS3\ZnS Stacks

“…This peak was identified by Dimitrievxska et al, 57 Guc et al, 55 and Schorr et al 59 as the E symmetry mode of the CZTS phase. However, other studies suggest that this peak is related to the ZnS secondary phase, 21,60 which was also identified by GIXRD, which can be due to the excess of this phase resulting from the thick ZnS top layer or due to the segregation of some unreacted particles within the CTS layer.…”

“…Secondary phases, such as ZnS, Cu x S, Sn x S y , and Cu x SnS y , are known to coexist within the CZTS films. , To remove these unwanted compounds, several researchers have suggested a sequential Cu 2 SnS 3 (CTS)/ZnS-based approach followed by an annealing treatment to produce single-phase CZTS films. This two-step synthesis process has been successfully explored using several techniques such as hydrothermal, spray pyrolysis, CBD, and sonochemical reactions, to produce CZTS films with adequate properties.…”

Effect of the stacking order, annealing temperature and atmosphere on crystal phase and optical properties of Cu2SnS3

“…290 cm −1 for CTS m , 303 cm −1 for CTS c and 337 cm −1 for CTS t ) 26 , 53 , 54 , numerous contradictions have been reported in the assignment of other modes related to the three CTS structures. These confusions concern mainly the modes at 351 cm −1 that was attributed either to CTS c 27 or to CTS t 55 – 57 , and at 352 cm −1 assigned to CTS m 19 , 26 , 29 , 49 , 57 , 58 or to CTS t structure 59 . Also, the peak located at 354 cm −1 was identified belonging to monoclinic structure of the CTS phase 50 , 54 , 60 , 61 , while Raadik et al described this mode as a signature of CTS c 30 .…”

“…CTS is also regarded as a precursor for the synthesis of CZTS materials used in solar cells devices 17 , 18 . A highly crystalline CZTS phase can be obtained by the optimization of the Cu 2 SnS 3 synthesis conditions and the addition of a ZnS layer 19 on top of CTS. Further sulfurization of the CTS\ZnS stacked layers at high temperatures will produce a reaction between the two films and the formation a single CZTS 20 phase.…”

“…Finally, the used precursors, the synthesis technique and process can also influence the final structure of the CTS films 26 . Various physical and chemical techniques have been employed to synthesize CTS films, such as pulsed laser deposition (PLD) 30 , spray pyrolysis 31 , thermal evaporation 32 , chemical bath deposition (CBD) 19 , solvothermal synthesis 33 , wet chemical method 29 and magnetron sputtering 34 . Magnetron sputtering is a physical technique for the synthesis of large-area and highly uniform films with controllable thickness and composition.…”