In recent years, Cu2ZnSn(S,Se)4(CZTSSe) materials have enabled important progress in associated thin‐film photovoltaic (PV) technology, while avoiding scarce and/or toxic metals; however, cationic disorder and associated band tailing fundamentally limit device performance. Cu2BaSnS4(CBTS) has recently been proposed as a prospective alternative large bandgap (~2 eV), environmentally friendly PV material, with ~2% power conversion efficiency (PCE) already demonstrated in corresponding devices. In this study, a two‐step process (i.e., precursor sputter deposition followed by successive sulfurization/selenization) yields high‐quality nominally pinhole‐free films with large (>1 µm) grains of selenium‐incorporated (
A series of copper thiospinel compounds, CuCo2S4‐
- NSF-PAR ID:
- 10454596
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of the American Ceramic Society
- Volume:
- 104
- Issue:
- 4
- ISSN:
- 0002-7820
- Page Range / eLocation ID:
- p. 1806-1813
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
x = 3) Cu2BaSnS4−x Sex (CBTSSe) for high‐efficiency PV devices. By incorporating Se in the sulfide film, absorber layers with 1.55 eV bandgap, ideal for single‐junction PV, have been achieved within the CBTSSe trigonal structural family. The abrupt transition in quantum efficiency data for wavelengths above the absorption edge, coupled with a strong sharp photoluminescence feature, confirms the relative absence of band tailing in CBTSSe compared to CZTSSe. For the first time, by combining bandgap tuning with an air‐annealing step, a CBTSSe‐based PV device with 5.2% PCE (total area 0.425 cm2) is reported, >2.5× better than the previous champion pure sulfide device. These results suggest substantial promise for the emerging Se‐rich Cu2BaSnS4–x Sex family for high‐efficiency and earth‐abundant PV. -
more » « less
Abstract Next‐generation electronics and energy technologies can now be developed as a result of the design, discovery, and development of novel, environmental friendly lead (Pb)‐free ferroelectric materials with improved characteristics and performance. However, there have only been a few reports of such complex materials’ design with multi‐phase interfacial chemistry, which can facilitate enhanced properties and performance. In this context, herein, novel lead‐free piezoelectric materials (1‐
x )Ba0.95Ca0.05Ti0.95Zr0.05O3‐(x )Ba0.95Ca0.05Ti0.95Sn0.05O3, are reported, which are represented as (1‐x )BCZT‐(x )BCST, with demonstrated excellent properties and energy harvesting performance. The (1‐x )BCZT‐(x )BCST materials are synthesized by high‐temperature solid‐state ceramic reaction method by varyingx in the full range (x = 0.00–1.00). In‐depth exploration research is performed on the structural, dielectric, ferroelectric, and electro‐mechanical properties of (1‐x )BCZT‐(x )BCST ceramics. The formation of perovskite structure for all ceramics without the presence of any impurity phases is confirmed by X‐ray diffraction (XRD) analyses, which also reveals that the Ca2+, Zr4+, and Sn4+are well dispersed within the BaTiO3lattice. For all (1‐x )BCZT‐(x )BCST ceramics, thorough investigation of phase formation and phase‐stability using XRD, Rietveld refinement, Raman spectroscopy, high‐resolution transmission electron microscopy (HRTEM), and temperature‐dependent dielectric measurements provide conclusive evidence for the coexistence of orthorhombic + tetragonal (Amm2 +P4mm ) phases at room temperature. The steady transition ofAmm2 crystal symmetry toP4mm crystal symmetry with increasingx content is also demonstrated by Rietveld refinement data and related analyses. The phase transition temperatures, rhombohedral‐orthorhombic (TR‐O), orthorhombic‐ tetragonal (TO‐T), and tetragonal‐cubic (TC), gradually shift toward lower temperature with increasingx content. For (1‐x )BCZT‐(x )BCST ceramics, significantly improved dielectric and ferroelectric properties are observed, including relatively high dielectric constantε r≈ 1900–3300 (near room temperature),ε r≈ 8800–12 900 (near Curie temperature), dielectric loss, tanδ ≈ 0.01–0.02, remanent polarizationP r≈ 9.4–14 µC cm−2, coercive electric fieldE c≈ 2.5–3.6 kV cm−1. Further, high electric field‐induced strainS ≈ 0.12–0.175%, piezoelectric charge coefficientd 33≈ 296–360 pC N−1, converse piezoelectric coefficient ≈ 240–340 pm V−1, planar electromechanical coupling coefficientk p≈ 0.34–0.45, and electrostrictive coefficient (Q 33)avg≈ 0.026–0.038 m4C−2are attained. Output performance with respect to mechanical energy demonstrates that the (0.6)BCZT‐(0.4)BCST composition (x = 0.4) displays better efficiency for generating electrical energy and, thus, the synthesized lead‐free piezoelectric (1‐x )BCZT‐(x )BCST samples are suitable for energy harvesting applications. The results and analyses point to the outcome that the (1‐x )BCZT‐(x )BCST ceramics as a potentially strong contender within the family of Pb‐free piezoelectric materials for future electronics and energy harvesting device technologies. -
more » « less
Abstract The quinary members in the solid solution Hf2Fe1−
δ Ru5−x Irx +δ B2(x =1–4, VE=63–66) have been investigated experimentally and computationally. They were synthesized via arc‐melting and analyzed by EDX and X‐ray diffraction. Density functional theory (DFT) calculations predicted a preference for magnetic ordering in all members, but with a strong competition between ferro‐ and antiferromagnetism arising from interchain Fe−Fe interactions. The spin exchange and magnetic anisotropy energies predicted the lowest magnetic hardness forx =1 and 3 and the highest forx =2. Magnetization measurements confirm the DFT predictions and demonstrate that the antiferromagnetic ordering (T N=55–70 K) found at low magnetic fields changed to ferromagnetic (T C=150–750 K) at higher fields, suggesting metamagnetic behavior for all samples. As predicted, Hf2FeRu3Ir2B2has the highest intrinsic coercivity (Hc =74 kA/m) reported to date for Ti3Co5B2‐type phases. Furthermore, all coercivities outperform that of ferromagnetic Hf2FeIr5B2, indicating the importance of AFM interactions in enhancing magnetic anisotropy in these materials. Importantly, two members (x =1 and 4) maintain intrinsic coercivities in the semi‐hard range at room temperature. This study opens an avenue for controlling magnetic hardness by modulating antagonistic AFM and FM interactions in low‐dimensional rare‐earth‐free magnetic materials. -
more » « less
Alkali halide postdeposition treatments (PDTs) have become a key tool to maximize efficiency in Cu(In
x Ga1−x )Se2(CIGS) photovoltaics. RbF PDTs have emerged as an alternative to the more common Na‐ and K‐based techniques. This study utilizes temperature‐dependent current–voltage (JVT ) measurements to study a unique RbF PDT performed in a S atmosphere. The samples are measured before and after 6 months in a desiccator to study device stability. Both samples contain Na and K which diffuse from the soda–lime glass substrate. A reference sample and a RbF + S PDT sample both show the development of a rear contact barrier after aging. The contact barrier is higher for the RbF + S PDT sample, leading to decreased current in forward bias. Series resistance is also higher in the RbF + S PDT device which leads to lower fill factor. However, after aging the reference sample has a larger decrease in open‐circuit voltage (V OC). Ideality factor measurements suggest Shockley–Read–Hall recombination dominates both samples.V OCversus temperature and a temperature‐dependent activation energy model are used to calculate diode activation energies for each sample condition. Both techniques produce similar values that indicate recombination primarily occurs within the bulk absorber. -
more » « less
Trigonal Cu2BaGe1−
x Snx Se4(CBGTSe) has recently gained interest as a potential photovoltaic absorber to target mitigation of antisite defect formation in Cu2ZnSn(S,Se)4. This study examines partial substitution of Cu by Ag as a potential approach to tune the properties of Ag‐incorporated CBGTSe in the following aspects: 1) phase stability and crystal structure as a function of Ag content; 2) film morphology and grain structure; 3) charge carrier properties; 4) band positions; and 5) charge carrier kinetics and recombination. Up to 20% of Cu can be substituted by Ag in CBGTSe, while above 20% a phase mixture appears. Increasing Ag content induces larger average grain size and reduced hole carrier densities. In contrast, photoelectron spectroscopy and photoluminescence measurements reveal negligible impact of Ag substitution on ionization potential (≈5.4 eV) and electron affinity (≈3.7 eV). Also, Ag content offers negligible impact on carrier lifetimes (few ns). Consistent with these fundamental properties, solar cells based on two different Ag/(Ag + Cu) ratios (≈0% and ≈20%) show comparable power conversion efficiencies (≈2.7–2.8%). These results indicate that CBGTSe films and solar cells may be less sensitive to Ag substitution compared to Cu2ZnSn(S,Se)4, at least at the current level of absorber and device optimization.
