Bandgap Tuning in BaZrS₃ Perovskite Thin Films

Abstract

Chalcogenide perovskites (such as BaZrS3) are gaining increasing attention for solar cells due to their lead-free nature and superior environmental stability. However, a major limitation of BaZrS3 is that its bandgap (∼1.75 eV) is significantly larger than the ideal bandgap (∼1.34 eV) required to achieve the maximum theoretical efficiency for a single-junction photovoltaic cell. In this study, we demonstrate the reduction in bandgap from 1.75 to 1.4 eV through in situ alloying of titanium (Ti) during chemical vapor deposition growth, forming BaZr1–x Ti x S3 thin films. Theoretical study showed good agreement with experimental observations, demonstrating feasibility of bandgap tuning of BaZrS3 films.

Time-resolved photoluminescence studies of perovskite chalcogenides

“…[4][5][6][7][8][9] These chalcogenide materials have direct band gap (E g ) tunable from the visible to near-infrared (NIR), strong optical absorption and luminescence, and reports of slow non-radiative recombination rates. [4][5][6][10][11][12][13] They feature inexpensive and non-toxic elements, combined with thermal stability up to at least 550 C. 14,15 We have recently demonstrated synthesis of large-area, atomically-smooth, epitaxial thin lms of BaZrS 3 by pulsed laser deposition (PLD) and molecular beam epitaxy (MBE). 16,17 Here we study single-crystal samples of the perovskite-structured material BaZrS 3 , and the related Ruddlesden-Popper phase Ba 3 Zr 2 S 7 .…”

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

“…With a band gap of around 1.9 eV and a high absorption coefficient on the order of 10 5 cm −1 , BaZrS 3 could be an ideal top-junction absorber material for a tandem solar cell. 9,10 On the other hand, BaHfS 3 has a higher band gap at 2.1−2.2 eV but a similarly high absorption coefficient and therefore may be more suitable for LED or water splitting applications. 9,11 One of the hallmarks of halide perovskites is their ease of synthesis, frequently involving solution processing at room temperature.…”

“…Of these combinations, BaZrS 3 has emerged as the most interesting for photovoltaic applications. With a band gap of around 1.9 eV and a high absorption coefficient on the order of 10 5 cm –1 , BaZrS 3 could be an ideal top-junction absorber material for a tandem solar cell. , On the other hand, BaHfS 3 has a higher band gap at 2.1–2.2 eV but a similarly high absorption coefficient and therefore may be more suitable for LED or water splitting applications. , …”

Machine Learning-Aided Band Gap Engineering of BaZrS3 Chalcogenide Perovskite

“…In a recent work, we successfully synthesized B site Ti-doped BaZrS 3 thin films. 22 In the present study, we have synthesized A site Ca-doped BaZrS 3 thin films using chemical vapor deposition (CVD). The methodology used for CVD synthesis of BaZrS 3 and Ca-doped BaZrS 3 thin films by the sulfurization of oxide precursor films is provided in the Methods section and has been illustrated in Figure 5a.…”

“…However, due to the non-perovskite ground state of BaZrSe 3 and the existence of a competing phase, the range of doping was limited. Additionally, partial replacement of the B cation (Zr) with Ti has shown a reduction in the band gap to ∼1.4 eV. , The range of doping was again limited by the non-perovskite ground state of BaTiS 3 . In the following, with the term doping, we will refer to isovalent alloying or atom lattice substitution of the same valency.…”