Electrodeposition of kesterite thin films for photovoltaic applications: Quo vadis?

Abstract

This paper aims at providing an updated overview of the main achievements in the development of solar cells based on Cu 2 ZnSn(S,Se) 4 (CZTS(Se)) Kesterite absorbers obtained by electrodeposition. Although undoubtedly challenging, the ultimate goal is to learn from the past works and build a solid framework for future advances in this field. What is the reason for the lower efficiency of electrodeposited CZTS(Se)-based devices (8%) compared to the world record efficiency achieved with a hydrazine-based solution approach (12.6%)? Can this gap be filled, or there are intrinsic limitations for this achievement? The review is divided into the three main electrodeposition approaches: sequential elemental layer, alloy co-deposition, and chalcogenide co-deposition. It is argued that considerable technical challenges must be overcome for the latter approach to be successfully applied.Plot of the record power conversion efficiencies of Kesterite sulfide-based solar cells obtained by electrodeposition (hollow dots), and world record efficiency of CZTS(Se)-based devices (full dots). The dashed line shows the 15% minimum efficiency threshold considered relevant for potential industrial application.

Electrodeposition and selenization of brass/tin/germanium multilayers for Cu2Zn(Sn1-xGex)Se4 thin film photovoltaic devices

“…This new record stimulates research on production techniques that are more environmentally benign and offers perspectives for application on a large scale. In this view, electrodeposition is a promising technique because it is a low-cost method that allows fast and continuous production on large substrates with good control over the composition and morphology [23]. Three approaches are commonly used to deposit the precursors for CZT(S,Se) thin films and are interesting for the development of CZTG(S,Se) thin films as well: successive deposition of elemental or binary alloy coatings, co-electrodeposition of the metals and co-electrodeposition of the metals and sulfur/ selenium.…”

“…Here, the variation in film thickness, responsible for in-depth inhomogeneity, was minimized by artificially enlarging the substrate with a current thief that surrounded the molybdenum substrate. Each deposition step can be optimized separately, enabling the deposition of uniform, dense films on large areas from stable electrolytes and short deposition times [23]. For the electrodeposition of brass and tin from aqueous electrolytes, several well-described electrolytes that are used on an industrial scale, are available [25].…”

Optimization of Cu2ZnSnS4 Absorber Layers via Sulfurization of Electrodeposited Cu-Zn-Sn Precursors for Photovoltaic Applications

“…Stacking of single metal layers lacks in-depth compositional homogeneity, even after annealing. Therefore, an extra preannealing step is required for the intermixing of elemental layers by this method [73].…”

“…Alternatively, direct electrodeposition of the chalcogenide compound (Cu-Zn-Sn-S) requires long deposition times and the electrolyte stability is often less comparing to electrolytes for metal alloy deposition [73]. On the other hand, metal alloy deposition for Cu-Zn-Sn metallic precursors provides a better in-depth compositional homogeneity.…”

“…Electrodeposition can be performed in aqueous solutions, organic solvents, molten salts and recently in ionic liquids [91][92][93]. In this work, we focus on electrodeposition from aqueous solutions using a three electrode cell to enable potential control of the deposition process.…”