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The influence of palladium doping on the structural, morphological, optical and electronic properties of formamidinium lead iodide perovskite films
(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
In this study, we investigated the effects of palladium (Pd) doping on the properties of formamidinium lead iodide (FAPbI<inf>3</inf>) perovskite films. Pd was doped at concentrations ranging from 0.5 to 2 % and coated onto indium tin oxide (ITO) glass substrates using a spin-coating technique. The crystal structure of the films was characterized using X-ray diffraction (XRD), revealing that Pd-doping reduces the hexagonal phase while increasing the cubic phase in the FAPbI<inf>3</inf> lattice. The optical properties were evaluated using ultraviolet–visible spectrophotometry (UV–Vis), showing changes in light absorption and a reduction in the energy gap with Pd incorporation. Scanning electron microscopy (SEM) was employed to examine the morphological properties of the films, indicating significant surface alterations and formation of larger grain sizes due to Pd incorporation. The electronic structure of perovskite films was thoroughly investigated using X-ray photoelectron spectroscopy (XPS). These findings demonstrate that Pd-doping significantly affects the structural, optical, and electronic properties of FAPbI<inf>3</inf> perovskite films, with potential implications for enhancing the performance of perovskite-based devices.
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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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Enhanced photocatalytic ability of CuO/Ni-doped TiO2 nanocomposite under visible light: Theory and experiment
(2025-09-01)
Bootchanont, Atipong
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Samerchue, Sorravich
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Sipae, Chanapong
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Zhao, Huali
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Noonuruk, Russameeruk
CuO/Ni-doped TiO<inf>2</inf> composite photocatalysts were synthesized using a co-precipitation method as the composite of Ni-doped TiO<inf>2</inf> (Ni–TiO<inf>2</inf>) with 0.5, 1.0, and 1.5 mol% of CuO. Composites with different CuO/Ni–TiO<inf>2</inf> ratios were studied to assess the influence of Ni and CuO on the crystal and local structure by X-ray diffraction (XRD) and X-ray absorption (XAS). The energy bandgap is investigated by UV–visible spectroscopy and is described by computational calculations using density functional theory (DFT). The correlation between the local site of Ni and the band structure will be analyzed and discussed by comparing the experiment and First-principle calculations. The photocatalytic activity of the CuO/Ni–TiO<inf>2</inf> systems is due to the absorption of radiation in the visible light region. The results indicated that 1.5 mol% of CuO contributes to the Ni–TiO<inf>2</inf> nanoparticles showing highest photocatalytic activity with rate constant of 0.03477 min−1 in the degradation of Rhodamine B, which could be attributed to the low recombination rate of the electron-hole pair, and decrease of the bandgap, increase in the concentration of •OH radicals in the solution, which is beneficial for improving the photo degradation rate of organic compounds.
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Pressure-induced phase transition and indirect band gap semiconductor in ZnSnN2: First Principles Calculation
(2025-01-01)
Sailuam, Wutthigrai
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Fongkaew, Ittipon
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Kongnok, Thanundon
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Kotmool, Komsilp
In this study, we investigate the phase transition of ZnSnN<inf>2</inf> from Pna2<inf>1</inf> to Pmnb using Density Functional Theory (DFT) across a pressure range of 0–70 GPa. Our results show the enthalpy intersection of the Pna2<inf>1</inf> and Pmnb phases at 19.28 GPa, indicating a phase transition from Pna2<inf>1</inf> to Pmnb ZnSnN<inf>2</inf>. The decrease in H<inf>v</inf> of the Pna2<inf>1</inf> phase under pressure before the phase transition is attributed to the reduction of the G and weakening covalent bond of Sn–N pair. The new Pmnb phase exhibits an increased Vickers hardness, Debye temperatures, and brittleness. Moreover, the band gap is an indirect band gap of 1.41 eV due to a rearrangement of lower energy levels for Sn s and p states in conduction band minimum (CMB) and N s and p states in valence band maximum (VBM) at Γ-point. These characteristics make The Pmnb phase promising candidates for applications were longer carrier lifetimes are needed. The mechanical properties, dynamical behavior, and electron localization functions (ELFs) have been investigated and discussed.
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Pressure and atomic size effects of IV cation on mechanical and electronic properties of Zn-IV-N2 (IV[dbnd]Si, Ge and Sn): First principles calculation
(2024-09-01)
Boonkhuang, Apiwat
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Kongnok, Thanundon
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Meethan, Weerachon
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Busayaporn, Wutthikrai
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Phacheerak, Kanoknan
Zn-IV-N<inf>2</inf> compounds, incorporating Si, Ge, and Sn, have emerged as pivotal materials for their mechanical and electronic properties, influencing optoelectronic devices and photovoltaic applications. Employing density functional theory (DFT), we comprehensively investigate the structural, elastic, mechanical, and electronic characteristics of ZnIVN<inf>2</inf> (IV[dbnd]Si, Ge, Sn) under ambient and pressure conditions up to 20 GPa. Our findings suggest that a larger atomic size of the group IV cation can be more easily compressed than a smaller size. The mechanical stability criteria and the phonon dispersion show mechanical and dynamic stability in both ambient pressure and under high pressure up to 20 GPa. The ZnSiN<inf>2</inf> and ZnGeN<inf>2</inf> exhibit linear increments in bulk modulus (B), shear modulus (G), and Young's modulus (E) under pressure, while ZnSnN<inf>2</inf> experiences a decrease in G and E. Notably, the energy gap of ZnSiN<inf>2</inf>, ZnGeN<inf>2</inf>, and ZnSnN<inf>2</inf> (4.62 eV indirect, 2.82 eV, 1.16 eV, respectively) increases with pressure due to higher N s orbital energy, approaching the UV region. In the valence band, a hybridization of N p and Si/Ge/Sn p orbitals is observed, offering opportunities to tailor the band gap for optimal applications in optoelectronic devices. Preferentially adjusting group-IV elements over group-II elements is recommended for optimizing band gap modulation. The correlation between larger atomic size and decreased band gap energy highlights the potential to fine-tune material properties through controlled variations in group-IV elements.
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Investigating the phase transition and properties of CaSiN2 under pressure based on first-principles calculations
(2023-12-01)
Meethan, Weerachon
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Kongnok, Thanundon
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Fongkaew, Ittipon
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Bootchanont, Atipong
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Saisopa, Thanit
In this study, we apply first-principles calculations to examine the pressure-induced phase transformation of CaSiN<inf>2</inf> in a range of pressure of 0–100 GPa. Its pressure-induced transitions at 1.3 GPa, 15.3 GPa, and 55.8 GPa followed the order of α- CaSiN<inf>2</inf> → β- CaSiN<inf>2</inf> → α- CaSiN<inf>2</inf> → γ- CaSiN<inf>2</inf>, for α- CaSiN<inf>2</inf> → β- CaSiN<inf>2</inf>, β- CaSiN<inf>2</inf> → α- CaSiN<inf>2</inf>, and α- CaSiN<inf>2</inf> → γ- CaSiN<inf>2</inf>, respectively. The stability of the phases of CaSiN<inf>2</inf> was confirmed based on calculations of the Born criterion of elastic stability. Its behavior transitioned in the sequence of brittle (0–1.3 GPa) → ductile (1.3–55.8 GPa) → brittle (55.8–100 GPa). The structure of its projected orbital band reflected insulating behavior by CaSiN<inf>2</inf> under a range of pressure of 0–55.8 GPa with a direct band gap, which transformed into metallic behavior by the γ- CaSiN<inf>2</inf> phase under pressures higher than 55.8 GPa, due to a shift in energy to higher levels around the Γ point of the N p orbitals and Si p orbitals. The Si-N bonds in CaSiN<inf>2</inf> were found to be covalent, while ionic bonding dominated the Ca-Si and Ca-N bonds in the range of pressure of 0–100 GPa. We also investigate and discuss its mechanical properties, Vickers hardness (H<inf>v</inf>), average sound velocity v<inf>m,</inf> and Debye temperature (θ<inf>D</inf>).
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Influence of pressure on elasticity, mechanical properties, and Li diffusion in battery electrode material LiCoO2: First-principles calculations
(2023-09-01)
Sailuam, Wutthigrai
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Fongkaew, Ittipon
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Busayaporn, Wutthikrai
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Klinkla, Rakchat
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Phacheerak, Kanoknan
This study used first-principles calculations based on density functional theory with generalized gradient approximation (GGA) of the Perdew Burke and Ernzerhof (PBE) parameterized form to investigate the influence of pressure on the structural, elastic, and mechanical properties of rhombohedral LiCoO<inf>2</inf>. The results indicate that rhombohedral LiCoO<inf>2</inf> remains stable up to 10 GPa. The calculated ground state properties agree well with experimental and other calculation data, validating the approach. Additionally, the calculated elastic constants, bulk modulus, Young's modulus, shear modulus, and Poisson's ratio at 0 GPa agree with previous results. The study found that all elastic constants continuously increase with increasing pressure. The deformation resistances along the axial direction are stronger than those in shape. The relationship between elasticity and length is such that C<inf>11</inf> > C<inf>33</inf>, indicating that the incompressibility along the a axis is stronger than that along the c axis. The analysis of Poisson's ratio (ν) and Pugh's criterion B/G strongly suggests that rhombohedral LiCoO<inf>2</inf> exhibits ductile behavior under pressure up to 10 GPa. The material is clearly anisotropic behavior, but the material exhibits improved isotropic behavior as pressure increases. Regarding Li ion diffusion in rhombohedral LiCoO<inf>2</inf>, the study found that the migration pathway for Li ions in rhombohedral LiCoO<inf>2</inf> is a direct route that extends from the V<inf>Li</inf> site to the closest Li site. The diffusion process is hindered by a diffusion energy barrier of 0.87 eV, which is in good agreement with available theoretical data. Furthermore, the Li ion diffusion energy barrier increases with pressure because the decrease in d<inf>mean</inf> and polyhedral volume, along with changes in angle and torsional distortion factors of CoO<inf>6</inf> octahedra, which can reduce the charging and discharging speeds of Li-ion batteries that use rhombohedral LiCoO<inf>2</inf> as the cathode material.
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Structural and photocatalytic properties and X-ray absorption spectroscopic study of BiVO4 nanoparticles incorporated with Fe synthesized by sonochemical method
(2022-11-01)
Wechprasit, Tirapat
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Bootchanont, Atipong
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Sailuam, Wutthigrai
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Wattanawikkam, Chakkaphan
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Kansaard, Thanaphon
In this work, Fe-incorporated BiVO<inf>4</inf> nanoparticles with different Fe-loading contents (0–4%) were synthesized via one-step sonochemical process. Crystal structure of all samples was investigated by X-ray diffraction technique (XRD). XRD patterns obviously show the main structure of monoclinic BiVO<inf>4</inf> structure. The secondary phase is found in the form of Fe-based oxide as a hematite Fe<inf>2</inf>O<inf>3</inf> phase at for Fe-loading contents ≥ 2%. Relevant chemical bonding of as-synthesized samples was carried out by Raman spectroscopy indicating the fundamental vibration with various vibration modes of VO<inf>4</inf>3− tetrahedron and V–O band, respectively. Morphological structure of pure BiVO<inf>4</inf> shows rod-like structure while 1–4%Fe-incorporated BiVO<inf>4</inf> display different morphologies. The chemical compositions and oxidation numbers of all elements of the samples were carried out via X-ray photoelectron spectroscopy (XPS). XPS spectra indicate the existence of all elements on their surface and the oxidation states of all elements are clearly scrutinized. Local structure of all samples was investigated to interrogate the local atomic site of Fe atoms by X-ray absorption spectroscopy (XAS). The normalized Fe K-edge XANES spectra of all samples indicate that the local atomic site of Fe atoms would not replace in local sites of either Bi or V sites in BiVO<inf>4</inf> crystal verified by simulated XANES spectra. However, the specific features of measured XANES spectra of all samples corresponds to the Fe K-edge XANES spectra of Fe<inf>2</inf>O<inf>3</inf> and BiFeO<inf>3</inf> structure suggesting that local structure of all samples are formed to Fe-based oxide between Fe<inf>2</inf>O<inf>3</inf> and BiFeO<inf>3</inf> structure. Fitting EXAFS spectra of 1–4%Fe-incorporated were practically conducted by artemis program with Fe<inf>2</inf>O<inf>3</inf> and BiFeO<inf>3</inf> used as structural models to identify local atomic environment of Fe atoms. Results show agreeable fitting with their structural models and reveal pertinent information of localization of Fe atoms. Optical properties of the samples were analyzed by UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS). DRS results exhibit the absorption edge in visible range of all samples. Meanwhile, influence of Fe loading contents into pure BiVO<inf>4</inf> displays to confirm the red-shift on the absorption edge in visible range to higher wavelength, which suggests the lower optical band gap of pure BiVO<inf>4</inf>. The optimized photocatalytic degradation of RhB was performed by 4%Fe–BiVO<inf>4</inf> with 82% decolorization under visible-light irradiation within 10 min and exhibited rate constant at 0.150 min−1.
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A first principles investigation on the structural, elastic, and mechanical properties of MAX phase M3AlC2 (M= Ta, Ti, V) as a function of pressure
(2022-03-01)
Sailuam, Wutthigrai
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Fongkaew, Ittipon
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Limpijumnong, Sukit
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Phacheerak, Kanoknan
This study investigated the structural, elastic, and mechanical properties of hexagonal M<inf>3</inf>AlC<inf>2</inf> (M = Ta, Ti, and V) within MAX phases by first-principles calculations. The considered properties of M<inf>3</inf>AlC<inf>2</inf> (M = Ta, Ti, and V) compounds at 0 GPa were in reasonable agreement with available experimental and other theoretical data. The elastic stability shows that no structural phase transition occurred in pressure up to 20 GPa for all compounds. The resistances to linear compression were more forceful than the resistances to compression in shape. The bulk modulus, shear modulus, and Young's modulus for M<inf>3</inf>AlC<inf>2</inf> (M = Ta, Ti, and V) compounds follow the order Ta<inf>3</inf>AlC<inf>2</inf> > V<inf>3</inf>AlC<inf>2</inf> > Ti<inf>3</inf>AlC<inf>2</inf>. The Bader charge analysis result shows the increasing of covalence bond in their structure after the pressure increased. Furthermore, Pugh's criterion B/G and Poisson's ratio v confirmed that the M<inf>3</inf>AlC<inf>2</inf> (M = Ta, Ti, and V) compounds had intrinsic brittleness. The sound velocity and Debye temperature of all compounds increased with pressure increasing. The bond stiffness and the shear anisotropy affected by pressure were reported and discussed.
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The pressure effect on the structural, elastic, and mechanical properties of orthorhombic MgSiN2 from first-principles calculations
(2021-10-01)
Bootchanont, Atipong
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Phacheerak, Kanoknan
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Fongkaew, Ittipon
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Limpijumnong, Sukit
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Sailuam, Wutthigrai
Pressure effect on lattice parameters, elastic moduli, Poisson's ratio, Cauchy pressure, elastic anisotropy, and Vickers hardness of orthorhombic MgSiN<inf>2</inf> by means of first-principles calculations based on density functional theory (DFT) by generalized gradient approximation (GGA) in the functional form by Perdew, Bruke, and Ernzerhof (PBE) of the exchange-correlation were presented. The structural properties, elastic moduli, B<inf>0</inf>/G, Poisson's ratio (ν) and Cauchy pressure under pressure up to 10 GPa were calculated. The optimized structural and ground state properties under ambient pressure were in agreement with the available experiments and other calculations. The orthorhombic MgSiN<inf>2</inf> was mechanically stable under pressure up to 10 GPa by the elastic stability criteria investigation. Under pressure, the relationship of elasticity in length was C<inf>33</inf> > C<inf>11</inf> > C<inf>22</inf>, indicating that it is easier to compress along the b-axis than along the a-axis and c-axis, respectively. The calculated bulk modulus, shear modulus, Young's modulus and Poison's ratio index all increased with an increase in the pressure. The B<inf>0</inf>/G, Poisson's ratio (ν) and Cauchy pressure analyses implied that orthorhombic MgSiN<inf>2</inf> was single crystal, and a critical pressure for brittle-to-ductile transition was found to be 2 GPa. The Cauchy pressure of {100} plane, {010} plane and {001} plane, Vickers hardness (H<inf>v</inf>) and the shear anisotropy as a function of pressure were investigated from the calculation.

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