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Characterization of Bi-doped FAPbI3 perovskite films investigated by X-ray absorption spectroscopy
(2025-12-01)
Wechprasit, Tirapat
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Bootchanont, Atipong
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Infahsaeng, Yingyot
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Wongjom, Poramed
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Wannapaiboon, Suttipong
A thorough investigation of perovskite structures formed through doping is essential for advancing the efficiency and stability of perovskite solar cells. In this study, Bi-doped FAPbI<inf>3</inf> perovskite films with varying Bi concentrations (0.5–2%) were fabricated using a spin-coating technique on ITO glass substrates. Then the films’ phase structure, local structure, and optical characteristics were analyzed. X-ray diffraction (XRD) analysis revealed that the pristine FAPbI<inf>3</inf> film exhibited both hexagonal and cubic phases, indicating structural instability. In contrast, Bi-doped FAPbI<inf>3</inf> films predominantly displayed a cubic perovskite structure, with a notable reduction in the XRD peak intensity corresponding to the hexagonal phase. UV–Vis spectroscopy showed that the undoped FAPbI<inf>3</inf> film had an absorption edge in the visible-near infrared range, while Bi-doping caused a redshift, indicating a reduction in the optical band gap. The calculated results show that optical band gaps decrease with increasing Bi, from a value of 1.49 (pure) to 1.43 (2% Bi) eV. X-ray absorption near edge structure (XANES) analysis confirmed the oxidation states of Pb2+ and Bi3+ ions across all samples, with Bi ions replacing Pb in the local structure. Photoluminescence (PL) measurements revealed an increased PL intensity with 1% Bi doping (7 105) compared with pristine FAPbI<inf>3</inf> (4.7 105), suggesting a reduction in carrier recombination. These findings demonstrate the potential of Bi-doping to stabilize perovskite structures with improved optoelectronic properties.
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Glass-sulfur composite cathodes: A new strategy for improving the performance of lithium-sulfur batteries
(2024-10-01)
Siriroj, Sumeth
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Padchasri, Jintara
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Montreeuppathum, Amorntep
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Sonsupap, Somchai
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Maensiri, Santi
In this study, we investigated the potential of glass-sulfur composites to improve lithium–sulfur battery (LSB) performance. Glass-sulfur composites were prepared by the precipitation method, and the effect of varying carbon black content was studied. The results showed that glass addition improved the battery performance due to the high ion-conductivity of its structural motif. The 75 % glass variant demonstrated the best results, in both the low carbon and high carbon cases. The cyclic voltammetry (CV) and electrical impedance spectroscopy (EIS) measurements showed that glass-sulfur composites had lower resistivity than pure sulfur, which was beneficial for battery performance. The XANES analysis revealed that the incorporated glass interacted with and modified the properties of sulfur, leading to a higher proportion of sulfur in the -1 oxidation state (S−1). This suggests that the high proportion of S−1 phase benefitted battery capacity. Overall, glass-sulfur composites prepared using the precipitation method and incorporating a high content of carbon show promise as a novel and improved cathode material for LSBs.
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Topology of boron substitutional defects in single-walled carbon nanotubes: A first-principles study
(2024-06-01)
Prachamon, Wutthisak
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Jaiboon, Oruethai
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Komin, Sittipong
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Ruttanapun, Chesta
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Limpijumnong, Sukit
This is a theoretical study of boron-doped single-walled carbon nanotubes. The same topology of primitive nanodomains, located at different positions on single-walled carbon nanotubes, leads to different electronic band structures. We propose a ϕ term. Density functional theory was corrected for van der Waals interactions and used to carry out the periodic boundary condition geometry optimization, where boron formed the topologies of primitive nanodomains. The calculated bulk structure and local structure spectroscopic parameters can be used for comparison with experimental results to confirm the theoretical models.
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Structural and Optical Properties of Mn-Incorporated BiVO4 Nanoparticles Synthesized by Sonochemical Process
(2022-01-01)
Wechprasit, Tirapat
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Kansaard, Thanaphon
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Bootchanont, Atipong
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Pecharapa, Wisanu
In this work, Mn-incorporated BiVO<inf>4</inf> nanoparticles with different Mn contents (0–5%) were synthesized by one-step sonochemical process. Structural phase of Mn-incorporated BiVO<inf>4</inf> nanoparticles was extensively carried out by X-ray diffraction technique. The XRD results show that the structural phase of BiVO<inf>4</inf> belongs to the monoclinic principal structure while the secondary phases of MnO, Mn<inf>2</inf>O<inf>3</inf>, and Mn<inf>3</inf>O<inf>4</inf> structures are noticed in Mn-loaded samples. Chemical bondings of Mn-incorporated BiVO<inf>4</inf> nanoparticles were characterized with Raman spectroscopy. Relevant chemical bondings confirm the existence of VO<inf>4</inf>3− tetrahedron and the V–O band by Raman spectra. Diffuse reflection spectroscopy and FE-SEM were employed to examine their optical and morphological properties, respectively. The results indicate that the incorporation of Mn can induce the red-shift of optical absorption edge in visible range, which can decrease the optical band gap of BiVO<inf>4</inf>. Morphology of all samples demonstrates the difference in shape of the compounds with the incorporation of Mn contents. Oxidation number and local structure of Mn-incorporated BiVO<inf>4</inf> nanoparticles were investigated by X-ray absorption spectroscopy. XAS results demonstrate that oxidation number of all elements correspond to Mn2+/Mn3+, Bi3+, and V5+ ions. The normalized Mn K-edge XANES spectra suggest that Mn atoms would not locate at the local site of Bi or V in BiVO<inf>4</inf> crystal because the specific feature of experimental spectra are inconsistent with simulated spectra, which is corresponded to XRD results indicating the formation of Mn-based oxide structures with various oxidation states.
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Characterization, X-ray absorption spectroscopic analysis and photocatalytic activity of Co/Zn co-doped TiO2 nanoparticles synthesized by one-step sonochemical process
(2021-10-01)
Mekprasart, Wanichaya
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Pavasupree, Sorapong
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Jayasankar, C. K.
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Ravuri, Balaji Rao
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Wattanawikkam, Chakkaphan
A novel one-step preparation of sonochemical method was applied to synthesize Co/Zn co-doped TiO<inf>2</inf> nanoparticles using a sonicator of 750 W, 20 kHz for 30 min at room temperature. The formation of the anatase TiO<inf>2</inf> phase for all as-prepared samples was observed from XRD results with a crystalline size in nanoscale. The use of ultrasound allowed for the successful doping of both Co and Zn into the TiO<inf>2</inf> lattice, which was confirmed by Synchrotron light including X-ray near edge structure (XANES) and Extended X-ray absorption fine structure (EXAFS) spectroscopy. Ti K-edge, Co K-edge, and Zn K-edge XANES spectra exhibited the dominating +4, +2, and +2 valence state of Ti, Co, and Zn in as-prepared samples, respectively. A detailed XANES and EXAFS data analysis give strong evidence that the Co/Zn dopants partially replace the Ti atom of the TiO<inf>2</inf> host. The Co/Zn co-doping extends the light absorption of the host to the visible region and restricts the e+/h+ recombination. The photocatalytic activity of samples was tested for degradation of Rhodamine B dye solution under visible light irradiation. The as-synthesized of the co-doped catalyst was presented as highly efficient, with 2.5 and 5 times dye degradation compared with single-doped and bare TiO<inf>2</inf>.
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The electrical properties of lanthanide doped potassium sodium lithium niobate based silicate glass
(2021-05-19)
Yongsiri, Ploypailin
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Sattayapom, Suchinda
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Senanon, Wipada
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Pengpat, Kamonpan
In this work, the electrical properties of ferroelectric glass-ceramics in the system of 75((K0.5Na0.5)0.94Li0.06)1-xErxNbO3 - 25SiO2 (75KNLNxEr - 25SiO2) with x varying between 0.005-0.01 mol% have been investigated. The Er2O3 is a lanthanide element that was found to promote the electrical and optical properties in many materials. The data from XRD pattern showed that the prepared glass-ceramics contained crystals of KNLNxEr solid solution, and the crystallite size slightly increased when increasing heat treatment temperature. For dielectric constant and dielectric loss at room temperature, the maximum values of about 304 at 1MHz with a dielectric loss below 0.01 was found in glass-ceramics without Er2O3 dopant. The dielectric value can be raised to 1750 in glass doped with 0.005 mol% of Er2O3 when the measurement temperature is increased. Finally, the oxidation states of glass-ceramics confirm by XANES showed that Er2O3 dopant was Er trivalent cations, and the erbium ions were not precipitated in oxide form.
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Nonlocal XANES pre-edge feature of FeTiO3 ilmenite-type at Ti and Fe K-edge
(2020-09-01)
Phoohinkong, Weerachon
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Boonyarattanakalin, Kanokthip
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Mekprasart, Wanichaya
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Pavasupree, Sorapong
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Pecharapa, Wisanu
The pre-K-edge feature of Ti and Fe XANES of ilmenite FeTiO<inf>3</inf> were investigated. The electronic structure of FeTiO<inf>3</inf> was examined based on the partial density of electronic state distribution on both local and nonlocal atoms. A strong contribution of nonlocal metal-metal intervalence electronic states of Ti and Fe pre-K-edge was observed in X-ray absorption near-edge structure (XANES) measurement. This observation agrees well with the calculated local state density. The nonlocal excitation transitions in the pre-edge feature contribute to local pre-K-edge at both Ti and Fe. Ti pre-K-edge consists of highly hybridized Ti-3d(t<inf>2g</inf>) with a small part of dipole-allowed 4p and a small 4s density transition state feature which is predominated by nonlocal of Fe-3d mixed with 4p state delocalized via O-2p as the main component peak. The peak feature at Ti-3d(e<inf>g</inf>) energy state is assigned to hybridization of Ti-3d(e<inf>g</inf>) and Ti-4p state contributed with nonlocal of the hybridized Fe-sp and the Ti-pd state. Fe pre-K-edge shows two main prominent transition peaks of hybridized Fe-pd state and the delocalized local Fe-sp with nonlocal Ti-3d(t<inf>2g</inf>) and 4p mixing states centered at 7112.38 and 7116.48 eV, respectively. The local and nonlocal excited transition energy states and density of both Ti pre-K-edge and Fe pre-K-edge features are corresponded with each other through the O-2p state transition pathway.
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Structural studies and photocatalytic properties of Mn and Zn co-doping on TiO2 prepared by single step sonochemical method
(2020-06-01)
Wattanawikkam, Chakkaphan
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Pecharapa, Wisanu
Titanium dioxide nanoparticles dual doped with zinc and manganese were prepared by the single step of sonochemical method using the sonicator with 20 kHz and 750 W for 30 min. Phase structure analysis results showed that the pure anatase phase was detected for all prepared samples. TEM analysis reveals the nanosized structure with uniformity of nanoparticles. The calculated bandgap energies change to be below the typical band gap energy of bare TiO<inf>2</inf> and single doped sample suggesting high ability to harvest visible light. X-ray absorption spectroscopy was conducted to investigate the electronics structure and to study the local structure of prepared samples. XANES results confirmed the existence of Ti4+ ions in all prepared samples with anatase crystal structure. EXAFS analysis indicates the Ti4+ site was substituted by Mn and Zn dopant ions. The photocatalytic performance was evaluated by degradation of Rhodamine B dye solution under visible light irradiation. The results revealed that the dually Mn–Zn doped TiO<inf>2</inf> sample exhibited excellent photocatalytic activity comparing to single doped and pure TiO<inf>2</inf>. The complete degradation of dye was achieved at optimum condition of 1 mol%-Zn and 2 mol%-Mn molar ratio. The highest photodegradation rate constant was found to be 0.0238 min−1, which is 10 times greater than pure-TiO<inf>2</inf> samples.
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Synthesis and characterization of CH3NH3PbI3 and CH3NH3PbI(3-x)Clx perovskite solar cell materials
(2019-11-18)
Kamonpha, Phitsamai
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Padchasri, Jintara
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Rujirawat, Saroj
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Sukkha, Usa
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Kidkhunthod, Pinit
The emerging of perovskite solar cell has attracted many interests in the synthesis and characterization of hybrid perovskite materials related to methylammonium iodide (MAI) due to various promising properties. In this work, we found a faster way to synthesize hybrid perovskite CH<inf>3</inf>NH<inf>3</inf>PbI<inf>3</inf> and CH<inf>3</inf>NH<inf>3</inf>PbI<inf>(3-x)</inf>Cl<inf>x</inf> (x = 0,1,2) powders from a different solvent in the preparation process of MAI precursor. In addition, it was found that in CH<inf>3</inf>NH<inf>3</inf>PbI<inf>(3-x)</inf>Cl<inf>x</inf> powders, as characterized by XRD and XAS, with a solid-state method employed Cl atoms cannot directly substitute for I in the perovskite (ABX<inf>3</inf>) structure.
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X-ray absorption spectroscopy analysis and photocatalytic behavior of ZnTiO3 nanoparticles doped with Co and Mn synthesized by sonochemical method
(2019-04-30)
Wattanawikkam, Chakkaphan
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Kansa-ard, Thanaphon
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Pecharapa, Wisanu
ZnTiO<inf>3</inf> (ZTO) as a perovskite structure doped with Co and Mn were fabricated by sonochemical process. Structural phase, chemical and local atomic structure and photocatalytic activity of the synthesized samples were characterized, by X-ray diffraction, by X-ray absorption spectroscopy and Rhodamine B (RhB) dye degradation. The XRD results revealed that the mixing phases of cubic and hexagonal zinc titanate phases were found in all samples. The X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure technique (EXAFS) have been used to identify the crystal and atomic local structure of prepared samples. The Fourier transform EXAFS results of these prepared samples agreed well with the model of Co and Mn substituting at the B-site of ABO<inf>3</inf> structure together with small cluster of CoO and Mn<inf>2</inf>O<inf>3</inf> cluster. The photocatalytic activity for rhodamine b dye degradation under visible light irradiation exhibited that the doped samples had the superior degradation compared to bare-ZTO sample. The results suggest that the incorporation of transition metal ions of Co and Mn dopants is an effective way to improve the catalytic efficiency of perovskite ZTO structure. The effect of different dopant ions and dopant concentration on the structural, chemical, optical and photocatalytic activity are discussed.

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