Metal Chalcohalides: Next Generation Photovoltaic Materials?

Abstract

Metal chalcohalides have recently been highlighted as so‐far overlooked semiconductors that could play an important role in the future of photovoltaics (PV). Indeed, the blooming field of emergent PV technologies is still in search for stable, efficient, and environmentally‐friendly light‐harvesting materials to be used either in single‐junction solar cells or multijunction devices in combination with silicon or another absorbers. Under the broad terms of metal chalcohalides, there exists a plethora of semiconductor materials with different chemical, structural, and optoelectronic characteristics. While some have already been implemented in solar cells with power conversion efficiencies up to 4–5%, others are only theoretically described. This perspective article offers a general overview of these materials as potential next‐generation absorbers in PV and also discusses possible limitations, not only related to intrinsic materials’ properties but also to processing conditions.

Colloidal Bismuth Chalcohalide Nanocrystals

“…The pursuit of nontoxic and robust inorganic semiconductors sets bismuth‐based materials as promising candidates for light‐harvesting purposes [1, 2] thanks to a presumably low toxicity [3, 4] and a promising (photo)chemical stability [5, 6] . Among the most investigated bismuth‐based semiconductors stand the oxides, by virtue of their potentially high chemical stability and low cost; however, their wide band gap prevents the absorption of a significant portion of the solar spectrum [7, 8] .…”

Understanding the Crystal Growth of Bismuth Chalcohalide Nanorods through a Self-Sacrificing Template Process: A Comprehensive Study

“…Chalcohalides are ternary compounds that have lately been re-emerging in the scientific literature. These materials present a combination of interesting electrical and optical properties, which have encouraged their study since 1960 in applications such as sensors, , actuators, radiation detectors, − photodetectors, energy storage devices, etc. − Lately, they have appeared in several reviews as potential candidates as substitutes for lead-based perovskites in photovoltaics. − They are attracting the attention of the scientific community, and the number of studies of these materials in greater detail is increasing. − Bismuth sulfoiodide (BiSI), in particular, has been scarcely studied for technological applications, but results in photovoltaics and ionizing radiation detectors are promising. ,− One of the main attractions of BiSI is that it is made of elements that are nontoxic and relatively abundant, , making their widespread application a more sustainable alternative when comparing it with other semiconductor materials, such as CdTe and CIGS . Moreover, the band structure of BiSI has been observed to have an indirect band gap of 1.57 eV, and it presents electronic characteristics similar to those of lead halide perovskites (which account for their remarkable performance in solar cells), i.e., an ns 2 configuration of the Bi 3+ atom and diffusivity of the band structure .…”

Emerging Chalcohalide Materials for Energy Applications

“…The incorporation of transition metals and chalcogen in lead-free perovskites has been proposed as a viable solution for improving the materials properties through bandgap engineering. ,− Likewise, heterovalent ions combine the excellent optical properties of both perovskites and chalcogenides since both positively and negatively charged ions addition are feasible bandgap tuning methods and thus the lifetime of charge carriers. − The semiconductor chalcohalides (V–VI–VII) consisting of thio-, seleno-, and halogens are discussed in the present review, e.g., V = Bi, Sb, Pb, Sn, Cu, Ag; VI = S, Se; VIII = Cl, Br, I. Among them, pnictogen chalcohalides are Bi- and Sb-based post-transition metal chalcohalides that comprise a trivalent heavy pnictogen (Bi/Sb) cation, a divalent (S/Se) chalcogenide, and monovalent (I/Br/Cl) halide anions.…”

“…The extensive developments in chalcohalide materials bring a necessity to review chalcohalides focusing on the materials design, their properties, film fabrication, and device fabrication while providing a perspective on future directions and potential applications in energy devices (Scheme ). The synthesis and applications of Bi- and Sb-based chalcohalide materials have been previously discussed as a part of dedicated book chapters − and reviews − as well as a brief overview of their potential in solar cell devices. − …”