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Synthesis and Characterization of Spinel Cobaltite (Co3O4) Thin Films for Function as Hole Transport Materials in Organometallic Halide Perovskite Solar Cells
摘要： Conventional inorganic p-type conductive oxides, e.g. NiO, CuOX, and CuCrOX, can serve as low-cost and efficient hole transport materials for wide bandgap organolead halide perovskites [e.g. MAPbI3], but low bandgap Sn-rich organometallic perovskites fail for (FASnI3)0.6(MAPbI3)0.4], where MA = (CH3NH3) and FA = (HC(NH2)2). In this work, we explore spinel Co3O4 based p-type conductive oxides as hole transport materials in organometallic halide MAPbI3 and (FASnI3)0.6(MAPbI3)0.4 perovskite solar cells. We examine the structural, crystalline, optical, electrical, photoelectrochemical, and surface chemistry properties of spin coated Co3O4 films without and with lithium doping. We find that lithium doping improves hole mobilities as well as film optical transparency and causes a lithium enriched overlayer (e.g. LiCoO2) forming at Co3O4 film surface. As a result, lithium doping can maximise the hole transport properties of Co3O4 in our inverted planar perovskite solar cells, achieving about 14% and 7% light-to-electricity power conversion efficiencies (PCEs) for perovskite halides MAPbI3 and (FASnI3)0.6(MAPbI3)0.4, respectively. This work underscores that cobaltite spinels hold promise in application as working HTLs for all kinds of organometallic halide perovskites.
关键词： cobaltite spinels,hole transport materials,doping,Co3O4,perovskite solar cells
更新于2025-09-23 15:19:57
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Gel-casting of MgAl <sub/>2</sub> O <sub/>4</sub> transparent ceramics using a common dispersant
摘要： The ethanolaminic salt of citric acid (commercial name Dolapix CE 64) has commonly been used as a dispersant for colloidal based ceramic forming process. In this paper, a surprise was presented that MgAl2O4 spinel slurries consisting of MgAl2O4 spinel nanoparticles and Dolapix CE 64 gelled in air at room temperature spontaneously. The MgAl2O4 spinel slurries with high solid loading (54 vol %) were prepared with Dolapix CE 64 and the green body with up to 57 % relative density was obtained. MgAl2O4 transparent ceramics with small grain size (0.92 μm) and high transmittance (81.7 % at 600 nm) were fabricated after pre-sintering at 1500 ℃ and hot-isostatic sintering at 1550 ℃.
关键词： transparent ceramics,spinels,gelcasting,slurries
更新于2025-09-19 17:15:36
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Estimation of structural composition of the inverse spinel ferrites using 57Fe-Zero Field Nuclear Magnetic Resonance
摘要： We have demonstrated 57Fe Zero Field Nuclear Magnetic Resonance (ZFNMR) as a powerful tool in determining the structural composition of nickel-cadmium spinel ferrites of various compositions of Ni1-x Cdx Fe2O4 from x = 0 to1, which are synthesized via one-step auto combustion technique. The XRD measurements confirm the phase purity of all the samples. Vibrating Sample Magnetometry (VSM) measurements show that saturation magnetization (MS) increases initially (up to x = 0.3) and then decreases for higher concentrations of cadmium. The Fe3+ ions in the inverted spinel ferrite distribute equally among two possible sites (tetrahedral A and octahedral B) with different hyperfine fields. Therefore for x = 0 under the assumption that Ni enters B sites, 57Fe NMR of Fe3+ ions yield two signals of equal integral intensities in spectral lines corresponding to these sites. Thus, for the sample series Ni1-x Cdx Fe2O4, the contribution of Fe3+ nuclei varies for A and B sub-spectra with the substitution of a non-magnetic Cd2+ ion. By measuring the Fe3+ distribution on A and B sites which is determined from relative spectral areas of A and B NMR sub-spectra the cation distribution is estimated and has been verified by the binomial distribution. Further, XRD Rietveld refinement results are also in good agreement with the composition estimated by NMR technique and the ideal composition. We have demonstrated the usefulness of NMR technique to quantify the accurate composition of the mixed spinel ferrite systems using Ni-Cd ferrite as a test case. Further, the estimated of inversion parameter (at around x = 0.4), for the studied system, obtained from ZFNMR, XRD, and VSM techniques are in excellent agreement with each other.
关键词： Structural composition,Binomial distribution,VSM,57Fe Zero Field NMR,mixed spinels
更新于2025-09-19 17:15:36
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Influencing Optical and Magnetic Properties of NiCr2O4 by the Incorporation of Fe(III) for Cr(III) Following Epoxide Gel Synthesis
摘要： With the objective of modifying the optical and magnetic properties of the spinel NiCr2O4, incorporation of 50 mol.% of Fe3+ for Cr3+ has been attempted following an epoxide-mediated gel synthesis. From the Le Bail re?nement of powder x-ray diffraction patterns of xerogels after calcination at 1000°C for 2 h in Fd-3 m space group, the lattice parameter of resultant spinels showed a marginal increase from 8.3117 (21) for NiCr2O4 to 8.3177 (26) A? for NiCrFeO4. The square morphology of the crystallites was observed in scanning electron microscopic images, and the energy-dispersive spectroscopy results con?rmed the uniform presence of Ni, Cr and Fe in these samples. Lattice fringes in high-resolution transmission electron microscopic images could be related to the cubic spinel structure. The optical band gap was found to decrease from 1.68 for NiCr2O4 to 1.41 eV for NiCrFeO4. Substitution of iron for chromium was found to reduce its catalytic ef?ciency for photo-degradation of aqueous rhodamine-6G (Rh-6G) dye solution under UV–visible radiation.
关键词： x-ray methods,Spinels,magnetic properties,calcination,sol–gel processes
更新于2025-09-09 09:28:46
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Magnetic, half-metallicity and electronic studies of Cd1-xZnxCr2Se4 chromium selenospinels
摘要： We have studied the magnetism of crystalline Cd1-xZnxCr2Se4 spinels with (0.35 ≤ x ≤ 0.55) under magnetic field up to 15 T. The total magnetic moment, Curie temperature, lattice parameter and exchange integrals were found to decrease with Zn substitution. Ab-initio calculations carried out using full potential augmented plane wave (FP-LAPW) method were performed to study the magnetic, and electronic structure using generalized gradient approximation (GGA) and the modified Becke-Johnson (mBJ) to correct the gap’s energy. The obtained results were in good agreement with the experimental ones. It is shown that there is a competition between ferromagnetic (FM) and antiferromagnetic (AFM) interactions: the super-exchange mechanism slightly increases the AFM contribution and keeps the FM the dominant mechanism in this range of substitution. From the density of states, we demonstrate that the system keeps the half-metallic state for the composition range 0.125 ≤ x ≤ 0.55 with 100% spin polarization. Our results highlight that it is possible to obtain a half-metallic semiconductor with tunable magnetic state which is promising for applications in spintronics.
关键词： magnetic competition,half-metallic,DOS,magnetization,mBJ,magnetic moment,Spinels
更新于2025-09-04 15:30:14