High‐Temperature Equilibrium of 3D and 2D Chalcogenide Perovskites

Abstract

Chalcogenide perovskites have been recently proposed as novel absorber materials for photovoltaic applications. BaZrS3, the most investigated compound of this family, shows a high absorption coefficient, a bandgap of around 1.8 eV, and excellent stability. In addition to the 3D perovskite BaZrS3, the Ba–Zr–S compositional space contains various 2D Ruddlesden–Popper phases Ban + 1ZrnS3n + 1 (with n = 1, 2, 3) which have recently been reported. Herein, it is shown that at high temperature the Gibbs free energies of 3D and 2D perovskites are very close, suggesting that 2D phases can be easily formed at high temperatures. The product of the BaS and ZrS2 solid‐state reaction, in different stoichiometric conditions, presents a mixture of BaZrS3 and Ba4Zr3S10. To carefully resolve the composition, X‐ray diffraction, scanning electron microscopy, and energy‐dispersive X‐ray spectroscopy analysis are complemented with Raman spectroscopy. For this purpose, the phonon dispersions, and the consequent Raman spectra, are calculated for the 3D and 2D chalcogenide perovskites, as well as for the binary precursors. This thorough characterization demonstrates the thermodynamic limitations and experimental difficulties in forming phase‐pure chalcogenide perovskites through solid‐state synthesis and the importance of using multiple techniques to soundly resolve the composition of these materials.

Enhancing the inherent stability of perovskite solar cells through chalcogenide-halide combinations

“…The results suggest that chalcogenide perovskite compounds may need to master the equilibrium of the two-phase structure at low temperatures, and finally be deposited and integrated into optoelectronic devices. 10 Ramanandan et al further investigated the thermodynamic distribution and study of BaZrO 3 (precursor) vulcanized by H 2 S. As the temperature rises, the overall structure is completely vulcanized at 1000 1C. The sensitivity of BaZrS to temperature was discussed.…”

“…It can be seen that most of the chalcogenide solar cells prepared in these experiments are synthesized by solid-state reaction. 10 A common processing method is to seal the element or binary chalcogenide precursors in ampoules and heat them at high temperatures for hours or days. This classical processing and growth method often requires a temperature of more than 1000 °C and a reaction cycle of several hours or even days, so that the reaction material can be completely diffused on a micron basis, to obtain a uniform crystalline material (Table 1).…”

“…The results suggest that chalcogenide perovskite compounds may need to master the equilibrium of the two-phase structure at low temperatures, and finally be deposited and integrated into optoelectronic devices. 10…”

“…It can be seen that most of the chalcogenide solar cells prepared in these experiments are synthesized by solid-state reaction. 10 A common processing method is to seal the element Fig. 3 The simulated lattice structure of the sulfide perovskite.…”

Syntheses, Crystal Structures, and Electronic Structures of Quaternary Group IV-Selenide Semiconductors

“…Further, their preparation in high purity shows a sensitive dependence with the reaction conditions. 17 Their synthetic preparation has predominantly involved the reaction of elemental or binary-chalcogenide reactants heated to 1200 °C inside sealed, evacuated quartz ampules. Recent studies have also demonstrated that lowertemperature reactions involving the use of sulfurization agents, e.g., boron sulfides or elemental sulfur, can also be effective in reactions with ternary oxides or other precursors.…”