Ti-Alloying of BaZrS₃ Chalcogenide Perovskite for Photovoltaics

Abstract

BaZrS 3 , a prototypical chalcogenide perovskite, has been shown to possess a direct band gap, an exceptionally strong near band edge light absorption, and good carrier transport. Coupled with its great stability, nontoxicity with earth-abundant elements, it is thus a promising candidate for thin film solar cells. However, its reported band gap in the range of 1.7–1.8 eV is larger than the optimal value required to reach the Shockley–Queisser limit of a single-junction solar cell. Here, we report the synthesis of Ba(Zr 1– x Ti x )S 3 perovskite compounds with a reduced band gap. It is found that Ti-alloying is extremely effective in band gap reduction of BaZrS 3 : a mere 4 atom % alloying decreases the band gap from 1.78 to 1.51 eV, resulting in a theoretical maximum power conversion efficiency of 32%. Higher Ti-alloying concentration is found to destabilize the distorted chalcogenide perovskite phase.

Chalcogenide Perovskites: Tantalizing Prospects, Challenging Materials

“…Sulfides: The most commonly synthesized sulfide perovskite is BaZrS 3 , which is reported to crystallize in the GdFeO 3 ‐type structure irrespective of the deposition method and temperature. [ 23,24,32,41,42,68–73 ] Similarly, BaHfS 3 has only been found in the GdFeO 3 ‐type phase by several authors. [ 23–25 ] By contrast, SrZrS 3 occurs in two distinct modifications depending on the growth process [ 70,92 ] —low‐temperature NH 4 CdCl 3 ‐type (α‐phase) and high temperature GdFeO 3 ‐type (β‐phase)—with the phase transition at about 980 °C.…”

Defect tolerance in chalcogenide perovskite photovoltaic material BaZrS3

“…Among them, BaZrS 3 having a band gap of about 1.8 eV [31,[33][34][35] is suited for making solar cells, in particular, when combined with silicon-based solar cells for twojunction tandem solar cells. Ti-doping has been attempted to optimize solar light absorption by reducing the band gap [31,36]. Thin films of BaZrS 3 have also been prepared with their electronic and optical properties being reported [37][38][39][40].…”

Chalcogenide Perovskites and Perovskite-Based Chalcohalide as Photoabsorbers: A Study of Their Properties, and Potential Photovoltaic Applications

“…A minute Ti-alloy concentration provided a suitable bandgap whereby the BaZrS 3 bandgap decreased from 1.78 to 1.51 eV by a (4) atom % alloy, bringing about a 32% maximum theoretical PCE for solar cells with a single junction. However, the chalcogenide perovskite phase experienced disruption triggered by the significant Ti-alloyed concentration [43]. The only way to avoid the distortion of the distorted chalcogenide perovskite from Wei et al results is to carefully select the Ti-alloyed concentration to suppress disruption and enhance its morphology.…”

“…Thus, amidst the chalcogenide perovskites, the highly investigated substance is BaZrS 3 . Based on the single-junction photovoltaic device, the BaZrS 3 energy gap is less optimal such as 1.74 eV [43]. It can be tailored by positively charged ions or negatively charged ions alloying together with the fragmentary replacement of Zr atoms [44].…”