Synthesis of BaZrS₃ Perovskite Thin Films at a Moderate Temperature on Conductive Substrates

Abstract

Chalcogenide perovskites are being considered for various energy conversion applications, not least photovoltaics. BaZrS 3 stands out for its highly stable, earth-abundant, and nontoxic nature. It exhibits a very strong light−matter interaction and an ideal band gap for a top subcell in a two-junction photovoltaic device. So far, thin-film synthesisnecessary for proper optoelectronic characterization as well as device integrationremains underdeveloped. Sputtering has been considered, among others, but the need for an annealing step of at least 900 °C has been a cause for concern: such a high temperature could lead to damaging the bottom layers of prospective tandem devices. Still, a solid-state fabrication route has already demonstrated that BaZrS 3 can form at much lower temperatures if excess S is present. In this work, sputtered Ba−Zr precursors capped by SnS are sulfurized at under 600 °C for 20 min. Although some Sn is still present at the surface after sulfurization, the resulting crystalline quality is comparable to samples synthesized at much higher temperatures. The results are rationalized, and the effect of key process variables is examined. This study represents the first successful synthesis of BaZrS 3 perovskite that is compatible with conductive substratesan important step forward for device integration.

Solution Deposition for Chalcogenide Perovskites: A Low-Temperature Route to BaMS3 Materials (M = Ti, Zr, Hf)

“…Comparotto et al utilized sputtering to create a Ba–Zr–S film that was subsequently sulfurized to create BaZrS 3 . Initially needing 900 °C to get high crystallinity, they later found that preventing oxide formation and supplying excess sulfur allowed the temperature to be dropped to around 600 °C. , Finally, low-temperature film fabrication has been achieved by first synthesizing BaZrS 3 at high temperatures and then depositing a film through pulsed laser deposition or by grinding and functionalizing the material to make a colloidal solution that can be coated. However, both methods have only produced films of low crystallinity without further heating. , …”

Solution-phase synthesis of the chalcogenide perovskite barium zirconium sulfide as colloidal nanomaterials

“…19 Most promisingly, film growth and crystallization at 600 1C has been achieved using a sputtering/ sulfurization approach. 20 Many of these techniques also require more complex and expensive equipment compared to the solution-phase growth and processing that is possible with the hybrid lead halide perovskites.…”

Low-Temperature, Solution-Based Synthesis of Luminescent Chalcogenide Perovskite BaZrS3 Nanoparticles

“…Chalcogenide perovskiteseponymously named for containing S, Se, or Te as the anion rather than a halideare an emerging frontier in Pb-free, inorganic perovskites with high stability. Promising optoelectronic properties have been identified for this material family, primarily from theory, including band gap values relevant for photovoltaics, a tolerance to deep defects, strong dielectric screening for generating free carriers with a long lifetime, favorable phonon properties for high-performance thermoelectrics, and desirable (isotropic) electron mobility for efficient charge transport. − Furthermore, a high density of chalcogenide p -states in the valence band maximum results in an extraordinarily high absorption coefficient, exceeding those of other solar technologies. , Importantly, increased covalent bonding in the crystal lattice relative to that in halide perovskites results in enhanced structural stability. ,− …”