Chalcogenides with stoichiometry ABCh₃ (Ch = S, Se) form in competing, complex crystal structures and are challenging to synthesize. These aspects may be obstacles for solar cell applications, but are opportunities for fundamental materials science because the distinct structures have distinct (and possibly useful) properties, and because the kinetic barriers to synthesis may enable long-lived metastable phases. The most widely-studied chalcogenide perovskite BaZrS₃, with band gap 1.9 eV, sits near the edge of phase stability. Alloying to reduce the band gap usually results in destabilizing the corner-sharing perovskite structure in favor of lower-dimensional structures with highly-anisotropic optoelectronic properties. Epitaxial film growth presents opportunities to stabilize structures that are thermodynamically unstable, and to explore the limits of phase stability and properties. I will present how we use methods of molecular beam epitaxy (MBE) to select between competing phases of BaZrSe₃: the perovskite with band gap near 1.5 eV, and a face-sharing hexagonal structure (h-BaZrSe₃) with large infrared birefringence. We can direct film growth towards one phase or the other by varying temperature, selenium potential, and/or the growth substrate. By choosing a substrate with rectangular symmetry in-plane, we demonstrate first-of-a-kind growth of fully-oriented h-BaZrSe₃ thin films with giant birefringence that can be measured directly polarized transmission spectrophotometry.

Chalcogenide perovskites are also distinguished by their vibrational properties. Their polar optical phonon frequencies are low, and the ionic contribution to their dielectric polarizability is high - they are among the most polarizable of all dielectric semiconductors with comparable band gap. I will present measurements of dielectric response and Hall mobility that demonstrate effective screening of charge defects. However, the phonon frequencies are not so low as for the halide perovskites. I will present Raman and photoluminescence spectroscopy measurements that suggest how and why phonon-assisted, non-radiative recombination (i.e., Shockley-Read-Hall) is much faster in chalcogenide perovskites than in their halide counterparts.

The relative dearth of chalcogenides that are stable in the perovskite structure points to a basic underlying fact, that the perovskite structure is most often found in ionic compounds (e.g., oxides and halides), whereas transition metal chalcogenides have a strong component of covalent bonding. Chalcogenide perovskites can be thought of as covalent semiconductors trapped in ionic structures. I will present explorations of the consequences of this tension, including X-ray spectroscopic measurements of directional bonding, and scanning transmission electron microscopy (STEM) data that suggest substantial band gap fluctuations throughout thin film samples. 

I will end by highlighting exciting directions for future research on complex chalcogenide semiconductors, including synthesis science, defect control, and advanced spectroscopy, that may enable future applications in photovoltaics and infrared photonics.

Chalcohalide are a family of inorganic semiconductors material that, thanks to a band gap generally between 0.7 eV and 2.2 eV, are emerging for photovoltaic application.[1–4] Chalcohalides have a the general formula MChX, in which M is one or more metal cations, Ch is a chalcogen (S^2-, Se^2-, Te^2-) and X is an halide (Cl^-, Br^-, I^-).[5] In this class of materials, the mixed metal chalcohalide Sn₂SbS₂I₃ has shown promising potential for photovoltaic application due to its suitable band-gap and stability. Initial studies on its photovoltaic performance were conducted by Nie et al., who fabricated a device based on this material, achieving a power conversion efficiency (PCE) of 4.04%.[6,7] This material is generally synthesized through different methods including solid state synthesis, microwave-assisted processes, solvothermal method, and heat-up procedure. However, these methods leads to a poor control over size and morphology of the final products. Here, we report the synthesis of this mixed-metal chalcohalide Sn₂SbS₂I₃ by hot injection method. Using this procedure for the chalcohalide, and exploiting the possibility to vary the parameter involved in the reaction, i.g. ligand-precursor chemistry, concentration variation of the reactive species, injection temparutre and annealing time,[8] we have achieved an accurate control of the size and the shape of the final crystals through. The particles showed a Cmcm crystal structure and rod-shaped morphology characterized by a lenght and width of 9,9 ± 3,0 µm and 0,9 ± 0,3 µm, respectively. The band gap is around 1.70 eV confirming the promising application for solar cell technologies. These results highlight the hot-injection approach as a promising synthetic method to synthesize Sn₂SbS₂I₃.

Colloidal metal halide perovskite nanocrystals have emerged as promising candidates for next-generation optoelectronic applications, including solar cells, light-emitting diodes (LEDs), and photodetectors. Their tunable optical and electronic properties, combined with facile solution-based synthesis, have brought lead and tin halide perovskites to the forefront of material research. However, due to environmental and health concerns associated with lead, tin-based perovskites have gained increasing attention, despite challenges posed by the instability of tin in its 2+ oxidation state.

In this work, we report recent advancements in the synthesis of tin halide perovskite nanocrystals, including CsSnI₃, CsSnBr₃, and FASnI₃, through precise control of precursor ratios and ligand chemistry. These developments enable the formation of highly stable, monodisperse nanocrystals with tunable optoelectronic properties. Notably, we observed the simultaneous formation of 2D Ruddlesden-Popper (RP) phases and 3D perovskite structures under similar synthetic conditions. Our studies highlight how the molecular ink plays a pivotal role in directing the growth and stability of these nanostructures.

We further demonstrate that by understanding the reaction mechanism, the precursor intermediate states, the selective formation of either 2D or 3D perovskite nanocrystals can be achieved, depending on the desired application. This control opens pathways for the development of tailored perovskite inks for optoelectronic devices, bridging the gap between fundamental colloidal chemistry and practical device implementation. Our findings provide critical insights into the growth mechanisms of tin halide perovskite nanocrystals, creating novel possibilities for their integration into future high-performance optoelectronic technologies.

Bismuth-based perovskite-inspired materials (Bi-PIMs) have garnered significant attention as promising alternatives to lead (Pb)-based perovskites due to their lower toxicity and higher environmental stability. These semiconductors, which include compounds like Cu₂AgBiI₆ and A₃Bi₂I₉, exhibit intriguing optoelectronic properties that make them suitable for photovoltaic applications. Bismuth (Bi)³⁺ shares similar electronic configurations with Pb²⁺, hinting to replicate the defect-tolerant electronic structure of lead-halide perovskites. This defect tolerance is crucial for reducing nonradiative recombination losses in Bi-based devices. Nevertheless, Bi-PIMs are also known to crystallize in disordered structures with a large number of surface defects/vacancies and grain boundaries compared to Pb-based perovskites, which explains their modest performance as photovoltaic absorbers.  [1] This raises important questions: How can we mitigate the density and detrimental effect of defects in Bi-PIMs? Could the defect-driven structural characteristics of Bi-PIMs be utilized to expand the applications of these materials in photonics beyond photovoltaics?

In the first part of the talk, I will first summarize our key findings on selected Bi-PIMs for photovoltaic applications. In particular, I will present recent results on our compositional engineering efforts to improve morphology and charge carrier transport in Bi-Pims, leading to enhanced efficiency in both outdoor and indoor PV. [2,3]

In the second part of the talk, I will demonstrate second harmonic generation (SHG) for two low-toxicity Bi-PIMs, Cu₂AgBiI₆ (CABI) and AgBiI₄ (ABI), using non-invasive nonlinear optical microscopy. The Bi-PIM with the largest number of cation vacancies, CABI, exhibits the most pronounced local inversion symmetry breaking, as assessed by the determination of the octahedral distortion angles. Consequently, CABI produces stronger SHG signals compared to ABI.  

Our findings not only advance our understanding of Bi-PIMs but also open new avenues for their application in photonics.

The expansion of the discovered material space of MHPs has recently moved towards the investigation of lead-free systems in order to overcome the concerns related to Pb-toxicity. While effective alternatives for PV applications rely mostly on tin-based compositions, several other phases containing different metals such as Bi, Sb, Cu, and Ge have been discovered and investigated.In many cases, such perovskites result ill-suited for PV devices but possess very appealing optoelectronic properties, which can be exploited in other applications. Among these systems, bismuth- and antimony-based perovskite derivatives of general formula Cs3M2X9 (M = Bi, Sb; X = Br, I) have shown strong technological potential, in particular in the area of photocatalysis (both for solar fuel generation and organic synthesis) and photodetection. In this contribution we will present our recent results in the synthesis of powdered, nanocrystalline and thin film based on Bi and Sb metal halides employing sustainable and scalable approaches. The prepared phases, where properties modulation has been achieved by alloying Bi/Sb, the halide site, as well as the A-site cation, were employied in different applicative fields ranging from detection, photocatalysis and non-linear optics [1-3].

The introduction of nanoscale materials has enabled substantial technological advancements, with halide perovskites emerging as a promising class of materials due to their ability to self-assemble into structures, promoting charge confinement. These materials are particularly attractive because of their straightforward synthesis and low-cost production. Depending on the degree of isolation between metal halides achieved by organic or inorganic cations, halide perovskites can exhibit two-dimensional, one-dimensional, or quasi-zero-dimensional configurations. Among these, quasi-zero-dimensional perovskite derivatives have garnered attention for applications spanning photovoltaics, thermoelectrics, lasers, photodetectors, memristors, capacitors, and light-emitting diodes (LEDs).^[1]

This work investigates the impact of sulphur doping on the thermal and electrical properties of bismuth-based perovskite derivatives. Sulphur doping was achieved by introducing bismuth tri-ethylxanthate into the precursor solution, with thin films fabricated using drop-casting or spin-coating techniques. Structural characterisation, employing X-ray diffraction, Raman spectroscopy, and grazing-incidence wide-angle X-ray scattering, confirmed the successful incorporation of sulphur into the crystal structure. Further insights into the material’s composition and morphology were obtained using X-ray photoelectron spectroscopy, CHNS elemental analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. An extensive study of UV-visible spectroscopy, photoluminescence, inverse photoemission spectroscopy, and ultraviolet photoelectron spectroscopy has provided a comprehensive understanding of the energy band gap. Results demonstrated that only the 1% sulphur doping reduced resistivity by two orders of magnitude. Furthermore, thermal voltage measurements revealed values exceeding 40 mV K⁻¹ at room temperature (~300 K) in both doped and undoped bismuth-based perovskite derivatives, highlighting the potential of these materials for thermoelectric applications.^[2]

Tin-based perovskites have emerged as a promising semiconductor due to their unique bandgap tunability and potential in all-perovskite multijunction tandems. Despite this potential, they currently lag in terms of stability and efficiency compared to their lead-based counterparts, primarily due to high defect densities from rapid thin-film formation and Sn vacancies caused by oxidation. As Sn oxidation is detrimental to device performance and stability, slower and controlled crystallization to reduce uncoordinated Sn is hypothesized to enhance device performance and stability. Researchers have extensively employed additive, cation, and solvent engineering to control the crystallization of Sn-based perovskites, though understanding of the process remains limited.

We aimed to deepen our understanding of the crystallization of Sn-based perovskites by measuring the photoluminescence (PL) while casting films to quantify the rate of crystallization and additional intermediate phases that may form. Utilizing additive engineering and in situ PL, we demonstrate we are able to significantly decrease crystallization rate relative to FASnI3 and PEA0.15FA0.85SnI3. Additionally, we are able to preferentially orient FASnI3 along the [001] and [010] planes, indicative of more controlled crystal growth. Additionally, we are able to grow FASnI3 thin films completely at room temperature, minimizing the amount of added energy into the system to oxidize Sn(II). Upon exposure to ambient conditions, x-ray photoelectron spectroscopy (XPS) measurements have shown increased stability of the engineered FASnI3 with significantly less Sn(IV) content compared to pure FASnI3 and 10.48% power conversion efficiency when implemented into a p-i-n solar device.

Despite the potential of tin-based perovskites (Sn-PVKs), these materials face challenges such as defect formation and Sn²⁺ oxidation or non-uniform film formation, which limit their performance and stability when applied to optoelectronic devices. The integration of  crystallization control and dimensionality modulation emerge as essential strategies to enhance the stability  and performance in both material and devices.   Here we present recent advancements in addressing Sn-PVKs’ challenges through these strategies, including the use of thiophene-2-ethylammonium halides (TEAX, where X = I, Br, Cl). The control on the synthetic conditions enables the dimensionality modulation of Sn-PVK microcrystals. In particular, using TEA+ as an organic cation, the formation of 2D-TEA₂SnBr₄ and highly luminescent 0D-TEA₄SnBr₆ microstructures was achieved, showcasing tailored optical properties for optoelectronic applications [1].  In parallel, the use of TEAX as an additive enhances FASnI₃ crystallization, suppresses Sn²⁺ oxidation, and boosts solar cell power conversion efficiency (PCE) from 6.6% to 12%. These additives also improve operational stability, with solar cells retaining over 95% of their initial PCE after 2000 hours of continuous operation under simulated sunlight [2]. The mechanisms of the unique FASnI₃-TEAX solar cells enhanced stability under ambient conditions will be highlighted. This includes insights into environmental factors such as humidity, applied voltage, and illumination, which influence the reversible decay and recovery of device performance.   Our analysis provides a comprehensive approach to unlocking the full potential of Sn-based perovskites in next-generation photovoltaics.

Tin-based perovskites (Sn-PVK) have emerged as one of the most promising lead-free alternatives for the development of efficient and environmentally friendly photovoltaic technologies. Despite their potential, the performance of Sn-PVK solar cells is severely limited by a high density of bulk and surface defects. These defects are primarily attributed to the rapid crystallization of the perovskite and the tendency of Sn²⁺ to oxidize into Sn⁴⁺, which creates lattice vacancies and significantly degrades device performance. The introduction of thiophene-2-ethylammonium halides (TEAX, where X = I, Br, and Cl) has been demonstrated as a strategy to improve the crystallization of FASnI₃, a common tin-based perovskite. When used in solar cells, these films present an improved operational stability maintaining >95% of the initial power conversion efficiency (PCE) after >2000 h in N₂ in continuous operation under 1 sun illumination. However, the evolution of the FASnI₃-TEAI solar cell parameters changes when carried out under ambient conditions.

In this work we present ongoing research to explore the mechanisms underlying the decay and subsequent recovery of the performance of FASnI₃-TEAI solar cells under ambient conditions. By analyzing the influence of environmental factors such as humidity, applied voltage, and illumination on device behavior, we aim to provide a better understanding of this unique phenomenon.

Tin halide perovskite solar cells (Sn-PSCs) are emerging as strong candidates to replace Pb-based perovskite solar cells (Pb-PSCs) due to their excellent optoelectronic properties and reduced toxicity. However, Sn-PSCs exhibit significantly lower efficiencies in comparison to Pb-PSCs due to, among other issues, the high voltage losses, which are nearly double the observed values in Pb-based PSCs.

On this basis, we designed and synthesized two novel fullerene derivatives, namely C₆₀-1 and C₆₀-2, functionalized with different fluorinated moieties, and incorporated them as interlayers between the perovskite and the C₆₀ electron transport layer. The LUMO levels of C₆₀-1 and C₆₀-2 at -3.98 eV and -4.01 eV, respectively, exhibited better band alignment with the conduction band of the tin perovskite layer (-3.92 eV) compared to C₆₀ (-4.05 eV). This enhanced alignment minimized the energy level mismatch, significantly improving the overall device performance. Additionally, the fluorinated functionalization conferred an extra degree of hydrophobicity enhancing the operational stability of the devices without any encapsulation in ambient atmosphere conditions. Consequently, the efficiency of the devices increased from 9.3% for the reference device to 10.5% and 11.0% for the devices containing the C₆₀-1 and C₆₀-2 interlayers, respectively. These results highlight the potential of functionalized fullerenes to mitigate voltage losses and improve the performance and stability of Sn-PSCs, paving the way for future advancements in their design and development.

Pnictogen-based semiconductors have gained increasing attention as potential nontoxic alternatives to lead-halide perovskites [1]. This is because of their ability to replicate key features of the electronic structure of lead-halide perovskites, which is believed to be conducive towards achieving defect tolerance, whilst overcoming the toxicity and stability limitations. This talk discusses one such material, BiOI, for applications in X-ray detection.

The composition of heavy elements Bi and I leads to stronger X-ray attenuation than commercial Cd-Zn-Te and amorphous-Se, as well as lead-halide perovskites. We show that the high stopping power, as well as its large mobility lifetime products and low dark currents enable these devices to have a limit of detection >250x improved over commercial amorphous-Se and Cd-Zn-Te detectors. This can improve the safety of medical imaging, and we examine the fundamental reasons behind the properties of BiOI enabling this strong performance [2]. Finally, we discuss the key challenges to bring this technology to market [3].

Luminescent zero-dimensional (0D) antimony halide (Sb–X) hybrids showcase emissive properties (emission peak position; photoluminescence quantum yield (PLQY)) that are heavily influenced by the local metal halide geometry/site asymmetry. However, achieving control over this local geometry has proven synthetically challenging due to the variety of coordination geometries that the Sb–X units can adopt. As a result, establishing a clear structure–luminescence relationship in 0D Sb–X hybrids has been difficult. This study is an attempt to draw a structure–luminescence relationship by controlling the Sb–X geometry utilizing 2D cadmium halide hybrids as the host that serves as a framework for incorporating emissive Sb3+ dopants. By selecting different organic cations, the local metal halide geometry/distortion within the host hybrids can be tuned, which in turn modulates the luminescent properties of the Sb3+ dopants. A distinct structure–luminescence relationship is observed: as the local metal halide distortion increases, the emission peaks shift to longer wavelengths (red-shift), and the PLQY improves. DFT calculations of the doped compounds, which explore the structural and electronic properties in both the ground and excited states, help clarify the luminescence mechanism and the reasons for varying luminescence efficiency (PLQY). This study provides deeper insight into the luminescence mechanisms, emphasizing the significance of structural distortions in both the ground and excited states of Sb3+-doped 2D cadmium halide hybrids. The experimental and computational findings are valuable for developing a clearer structure–luminescence relationship and for guiding the rational synthesis of 0D Sb halide hybrids.

Perovskite nanocrystals (NCs) are well known for their exceptional tuneable optical and electronic properties. They can be engineered at the nanoscale to optimize their interaction with light, improving the efficiency of the absorption, transfer, and conversion of energy.

Lead-free metal halide materials, such as Bi- and Sb-based NCs, having an A₃B₂X₉ (A = CH₃NH₃⁺, Cs⁺; B = Sb³⁺ or Bi³⁺, X = Cl^–, Br^–, I^–) stoichiometry, have been proposed as good candidates for heterogeneous photocatalysis thanks to their higher chemical stability and better performance than those of Pb-based perovskite NCs. In this context, the ability of colloidal layered structures Cs₃Sb₂Br₉ NCs for the photoreduction of p-substituted benzyl bromide substrate to produce C-C coupling products and the key role of the surface chemistry in facilitating the interaction between the NC and the substrate will be discussed. Moreover, they showed promising activity towards the photocatalytic degradation of organic dyes with good recyclability, preserving their performance and structural properties.

Recently, we have explored the (photo)catalytic potential of a family of perovskite oxides Ca_xSr_01-xTiO₃ (x=0-1) doped with iron and cobalt the sublattices. The pollutant degradation (organic dyes) and clorates reduction activity will be also discussed for water remediation.

Double perovskite (DP) nanocrystals (NCs) are promising lead-free materials for applications in photovoltaics, light-emitting devices, and plastic scintillators. The state-of-the-art DP NCs, Cs_1.92Ag_0.2Na_0.75K_0.07InCl₆ doped with 0.5% Bi (CANKBIC), achieve a photoluminescence (PL) quantum yield (QY) of ~70% [1]. However, their excited-state fine structure remains unexplored. In this work, we present temperature- and magnetic field-dependent PL dynamics of CANKBIC NCs, providing evidence for a luminescent state split into three distinct levels with lifetimes ranging from a few ns to ms.

Synthesized CANKBIC NCs exhibit PL centered at 2.0 eV and a multiexponential decay with an average PL lifetime (τ_avg) of 4.7 µs at room temperature. The PL originates from self-trapped excitons involving BiCl₆ and AgCl₆ octahedra, though the fine structure of the emissive state remains unexplored. As the temperature drops below 150 K, the τ_avg triples—a phenomenon previously attributed to the suppression of non-radiative decay, suggesting near-unity QY below this temperature [2]. At temperatures below 15 K, the τ_avg further increases reaching values of ~ms at 6 K. We interpret these results as a fingerprint of a fine structure in the emissive state, with a lower lying forbidden (dark) and a higher lying allowed (bright) state. Crucially, the analysis of the temperature dependent PL lifetimes and the decay amplitudes, reveals that the dark state is further split into two states exhibiting very different transition probabilities. At 6 K, applying a magnetic field shortens the PL lifetime, consistent with field-induced mixing between the dark states. We attribute the fine structure to a combined effect of electron-hole exchange interaction and spin-oribit coupling in a low symmetry environment, similar to what is observed in e.g. Cu(I) molecular complexes [3].

This study unveils the previously unobserved excited-state fine structure of DP NCs, contributing new insights into their photophysical behavior.

As a new class of semiconducting materials with excellent optoelectronic properties, metal halide perovskites have been applied in various fields such as solar cells, photodetectors, and electroluminescence. However, the toxicity of the lead element contained in these materials limits their application scenarios. Tin, a low-toxic element in the same main group as lead, is considered the most suitable alternative to lead. However, the performance of tin perovskite materials is currently far inferior to lead-containing materials, especially in terms of the short carrier lives and low open-circuit voltages of photovoltaic devices. Current research community generally attribute these phenomena to the material defects of tin perovskites, but the nature and regulation of these defects remain obscure. Under the guidance of theory, we have systematically studied this issue for tin perovskites from both aspects of bulk and surfaces, and prepared a series of high-quality single crystal and thin film samples. We directly characterized the types of defects, their concentrations and influence on semiconductor properties, revealing that the dominant defects in tin perovskites are not directly caused by oxidation of Sn2+. We found that substituted thiourea molecules as Lewis-base ligands can deactivate the Sn2+ 5s electron pair and create an appropriate intermediate phase structure, thereby slowing down the crystallization rate, inhibiting surface and bulk defects of the crystal, and obtaining high-quality thin films. On the other hand, by decorating the thin-film surfaces with molecular dipoles but not changing the bandgap of perovskite layer, we elevated its conduction band minimum (CBM) to better match the energy level of the electron transport material (ETM). The above measures have rendered thin films of tin perovskite with charge carrier lifetimes longer than 0.5 μs and diffusion lengths on the micrometer scale, and boosted the open-circuit voltage of solar cell devices to 1.0 V (only ~0.1 V loss), approaching the level of lead-containing materials. The energy conversion efficiency reached 16%, setting a new performance record for lead-free perovskite solar cells. Their stabilities are also significantly enhanced, demonstrating a promising application prospect.

In recent years, substantial efforts have been made, dedicated to identifying lead-free perovskites that retain the remarkable optoelectronic properties of lead-based perovskites while enhancing stability and reducing toxicity. Numerous substitution strategies have been explored, resulting in promising new materials, like for example halide double salts. This class of materials, have demonstrated high potential, with compounds like AgBiI₄ and Ag₃BiI₆ showing some of the highest power conversion efficiencies among lead-free photovoltaic materials[1–4]. Yet, these materials have been a challenge to model due to the existence of vacancies, and partially occupied Ag- and Bi-sites in their crystal lattice. Recently, we developed a symmetry-based approach to create atomistic models that allow the accurately description of their electronic structure and optical properties[5]. Here, we employ this approach to investigate atomic substitutional engineering in order to explore the phase space of Ag-In halide double salts and design a direct band-gap material in analogy with the case of Cs₂AgInCl₆ double perovskite[6]. By substituting Bi³⁺ with In³⁺ in a reduced-symmetry model of AgBiI₄, our first-principles calculations for AgInI₄ show a direct bandgap within the visible range (1.72 eV), close to the optimal range for indoor photovoltaic applications. This value is comparable with the indirect bandgap (1.68 eV) of the Bi-based ternary compound, suggesting a potential advantage for the In-based material in photovoltaic efficiency under specific conditions. To confirm this, we evaluate the spectroscopic maximum limited efficiency of AgInI₄ compound under AM-1.5G solar irradiance and LED irradiance using the LED-B4 standard. Our findings indicate that the In-based compound under-perform with respect to Bi-based for thin-film thickness of around 500 nm, though slightly improved performance is observed at thicknesses of above 1.5 μm. Based on these predictions, we set to synthesize the hypothetical In-based double salt and the resulting thin film exhibited transparency at room temperature, not matching our initial hypothesis. This prompt us to explore the possibility that more stable phases exist within the complete Ag-In-I phase space. By employing a systematic materials screening process within the Materials Project database, [7] we identify new phases that are more stable than the AgInI₄ phase designed starting from AgBiI₄. These phases exhibit direct bandgaps that are larger than 3.0 eV. While these hitherto unknown phases may not be suitable for photovoltaic applications, their transparency, dispersive electronic bands and well-defined band edges position them as promising candidates for other applications that require wide-bandgap semiconductors. Overall, our exploration of the Ag-In-I phase space broadens the opportunities for the development of environmentally friendly materials for optoelectronic applications where wide bandgap semiconductors are required.