Synthesis and Characterization of Cu2ZnSnS4 Thin Films Obtained by Combined Magnetron Sputtering and Pulsed Laser Deposition.

Mohamed-Yassine Zaki,Claudia Mihai,Florinel Sava,Iosif-Daniel Simandan,Nicu Becherescu,Alin Velea,Angel-Theodor Buruiana,Aurelian-Catalin Galca

doi:10.3390/nano11092403

Abstract

Cu2ZnSnS4 (CZTS) is a complex quaternary material, and obtaining a single-phase CZTS with no secondary phases is known to be challenging and dependent on the production technique. This work involves the synthesis and characterization of CZTS absorber layers for solar cells. Thin films were deposited on Si and glass substrates by a combined magnetron sputtering (MS) and pulsed laser deposition (PLD) hybrid system, followed by annealing without and with sulfur powder at 500 °C under argon (Ar) flow. Three different Cu2S, SnS2, and ZnS targets were used each time, employing a different target for PLD and the two others for MS. The effect of the different target arrangements and the role of annealing and/or sulfurization treatment were investigated. The characterization of the absorber films was performed by grazing incidence X-ray diffraction (GIXRD), X-ray reflectometry (XRR), Raman spectroscopy, scanning electron microscopy, and regular transmission spectroscopy. The film with ZnS deposited by PLD and SnS2 and Cu2S by MS was found to be the best for obtaining a single CZTS phase, with uniform surface morphology, a nearly stoichiometric composition, and an optimal band gap of 1.40 eV. These results show that a new method that combines the advantages of both MS and PLD techniques was successfully used to obtain single-phase Cu2ZnSnS4 films for solar cell applications.

Highlights

Cu2 ZnSnS4 (CZTS) is a strong material candidate for next-generation solar energy converters due to its high absorption coefficient and optimal band gap [1]
Two targets were mounted in cathodic sprayers, and one in the pulsed laser deposition (PLD) carousel, and the thin films were synthesized on silicate glass and Si/SiO2 substrates
Three CZTS films were deposited at room temperature on each type of substrate by fixing a target to be deposited by PLD and the two others sputtered by magnetron sputtering (MS), all deposits taking place simultaneously

Summary

Introduction

Cu2 ZnSnS4 (CZTS) is a strong material candidate for next-generation solar energy converters due to its high absorption coefficient and optimal band gap [1]. Vacuum techniques can be complex and require high energy, they are collectively regarded as a solution to overcome issues related to time consumption, cracks, and poor crystallinity of more used chemical routes [3,4] They offer the possibility to control the structural and morphological properties of the thin films [5]. PLD is a simple and versatile technique that is commonly used for depositing thin films of a very wide range of materials on a vast variety of substrates [8,9]. In the MS technique, different parameters (pressure, power, deposition time, etc.) can be varied in order to determine the optimal conditions to obtain high-quality films. The effect of heat treatment with and without sulfurization on the properties of the CZTS thin films was investigated

Materials and Methods

Results and Discussion

The transmittance measurements were performed