Aqueous-Based Binary Sulfide Nanoparticle Inks for Cu2ZnSnS4 Thin Films Stabilized with Tin(IV) Chalcogenide Complexes

Abstract

Cu2ZnSnS4 (CZTS) is a promising semiconductor material for photovoltaic applications, with excellent optical and electronic properties while boasting a nontoxic, inexpensive, and abundant elemental composition. Previous high-quality CZTS thin films often required either vacuum-based deposition processes or the use of organic ligands/solvents for ink formulation, which are associated with various issues regarding performance or economic feasibility. To address these issues, an alternative method for depositing CZTS thin films using an aqueous-based nanoparticle suspension is demonstrated in this work. Nanoparticles of constituent binary sulfides (CuxS and ZnS) are stabilized in an ink using tin(IV)-based, metal chalcogenide complexes such as [Sn2S6]4−. This research paper provides a systematic study of the nanoparticle synthesis and ink formulation via the enabling role of the tin chalcogenide complexing power, the deposition of high-quality CZTS thin films via spin coating and annealing under sulfur vapor atmosphere, their structural characterization in terms of nanocrystal phase, morphology, microstructure, and densification, and their resultant optoelectronic properties.

Fabrication of Cu2ZnSnS4 Light Absorber Using a Cost-Effective Mechanochemical Method for Photovoltaic Applications

“…The strongest band at 336 cm −1 was attributed to the A1 symmetry mode, which was ascribed to the vibration of sulfur atoms in the lattice [ 37 ]. These observed vibration peaks are consistent with the previously reported Raman peaks of CZTS material [ 38 , 39 , 40 ]. The Raman peaks for other secondary phases, such as binary and/or ternary phases, have been described in various studies; their vibrational bands are listed in Table S1 .…”

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

“…However, the sulfurized samples are still off-stoichiometric, rich in tin, and slightly poor in sulfur. The existence of tin in excess can cause the formation of the SnS or SnS2 secondary phases [49]. This explains the apparition of the peak at 320 cm −1 in both samples (Cu2S (PLD)/sulfurized and SnS2 (PLD)/sulfurized) in the Raman analysis, An estimation of the average atomic ratios of the four elements (Cu, Zn, Sn, and S), obtained from the energy-dispersive spectroscopy (EDS) analysis, in the as-deposited and sulfurized samples, is presented in Figure 5.…”

“…However, the sulfurized samples are still off-stoichiometric, rich in tin, and slightly poor in sulfur. The existence of tin in excess can cause the formation of the SnS or SnS 2 secondary phases [ 49 ]. This explains the apparition of the peak at 320 cm −1 in both samples (Cu 2 S (PLD)/sulfurized and SnS 2 (PLD)/sulfurized) in the Raman analysis, which can be definitely attributed to the SnS 2 phase.…”

Phase evolution of Cu2ZnSnS4 (CZTS) nanoparticles from in situ formed binary sulphides under solvothermal conditions

“…18 A robust method to achieve CZTSSe layers implies the deposition of pre-synthesized binary and ternary sulphide nanoparticulate inks onto a suitable substrate, followed by evaporation of the solvent, annealing under a controlled atmosphere and selenization. [28][29][30][31][32] While this solid phase route is widely explored, the conversion of binary to quaternary sulphides in the liquid phase has been poorly investigated, although this is an important underlying formation mechanism. Therefore, in the current paper, inorganic salts are selected that mainly lead to binary sulphides besides small amounts of CZTS particles during the early stages of particle formation.…”