Optical Absorption Performance Research Articles

Tunable optical properties of BAs/ZnO vdW heterostructure

Abstract Stacked heterostructures is an effective strategy for physical property modulation and application of novel two-dimensional materials. In this study, a heterostructure consisting of two-dimensional III-V group hexagonal BAs and monolayer of ZnO is presented. The minimum value of binding and cohesive energies screened the BB’ configuration. Phonon spectra and ab initio molecular dynamics (AIMD) simulations further demonstrated the kinetic and thermodynamic stability of the selected model. Most notably, the formation of the heterostructure greatly improves the optical absorption performance of the monolayer, especially in the infrared (IR) regions. At a compressive strain of -6%, the band alignment shifts from type I to type II, while the bandgap becomes dramatically smaller. Refraction and reflection coefficients in the IR region under compressive strain (-2% and -4%) modulation were enhanced significantly. Our results provide theoretical guidance for the design of high-performance photovoltaic devices and solar cells based on BAs/ZnO heterostructures.

Optimized Photothermal Conversion Ability through Interband Transitions in FeCoNiCrMn High-Entropy-Alloy Nanoparticles.

High-entropy-alloy nanoparticles (HEA-NPs) composed of 3d transition metallic elements have attracted intensive attention in photothermal conversion regions due to their d-d interband transitions (IBTs). However, the effect arising from the unbalanced elemental ratio still needs more focus. In this work, FeCoNiCrMn HEA-NPs with different elemental ratios among Cr and Mn have been employed to clarify the impact of different composed elements on the optical absorption and photothermal conversion performance. It can be recognized that the unbalanced elemental ratio of HEA-NPs can reduce the photothermal performance. Density functional theory calculation demonstrated that d-d IBTs can be changed by the different composed element ratios, resulting in a number of insufficient filling regions around the Fermi level (±4 eV). As a result, the HEA-NPs (FeCoNiCr0.75Mn0.25) with a balanced elemental ratio exhibit the highest surface temperature of 97.6 °C under 1 sun irradiation, and the evaporation rate and energy conversion efficiency could reach 2.13 kg·m-2·h-1 and 93%, respectively, demonstrating effective solar steam generation behavior.

Fe/LiNO3/TiN co–modified MgO for enhanced thermochemical energy storage performance in MgO/Mg(OH)2 cycles

MgO/Mg(OH)2 thermochemical energy storage can convert solar energy and industrial waste heat into forms that are easier to store and transport by cyclic hydration/dehydration reactions. To achieve excellent energy storage performance, cyclic stability and optical absorption capability of MgO/Mg(OH)2, Fe/LiNO3/TiN co–modified MgO were synthesized for energy storage cycles by wet-mixing method. The energy storage performance, cyclic stability and dehydration kinetics of Fe/LiNO3/TiN co–modified MgO were studied in dual fixed–bed system and simultaneous thermal analyzer. The experimental results show that the Fe and LiNO3 in the composite not only increase the hydration conversion of MgO by 6.3 times at 30 min, but also reduce the dehydration temperature and dehydration activation energy of Mg(OH)2 by 99.4 °C and 64 %, respectively. TiN overcomes aggregation of MgO and sustains the excellent porous structure, which results in only a 9 % decrease in energy storage performance of Fe/LiNO3/TiN co–modified MgO after 15 energy storage cycles. Subsequently, TiN significantly strengthens the optical absorption performance of Mg(OH)2 and photothermal temperature under xenon-lamp simulated sunlight radiation. Furthermore, density functional theory calculation reveals that Fe and Li enhance the adsorption of H2O on MgO model and reduce energy barrier for hydration reactions by 62.76 %, while TiN effectively inhibits MgO clusters migration within the material and enhances the optical absorption coefficient. Hence, Fe/LiNO3/TiN co–modified MgO shows significant research value in MgO/Mg(OH)2 energy storage process.

Reconfiguring the Optical Selection Rule in Ultramicrotome‐Crafted Vertically Aligned InSe Ribbons

AbstractDue to the high carrier mobility and direct bandgap character, indium selenide (InSe) exhibits great advantages for advanced optoelectronic applications. However, the unique optical section rule in InSe weakens the light‐matter interaction when the electric field of illuminated light is perpendicular to the c‐axis of planar InSe flake. To overcome this constraint, ultramicrotome technique is introduced to achieve vertically aligned InSe ribbons, aiming to reconfigure the optical paths for improved optical absorption and device performance. The well‐designed InSe ribbons are acquired with uniform morphology, showing an integrated structure free of cracks or fragments. First, the structural symmetry, crystal orientation, and optical anisotropy of InSe ribbon are carefully revealed by polarization‐dependent Raman spectrum, second harmonic generation (SHG), and photoluminescence measurements. Then, the back focal plane (BFP) imaging of photoluminescence distinguishes the in‐plane and out‐of‐plane dipole emission of InSe ribbons and planar InSe flakes, respectively. Notably, the ribbon exhibits new PL peaks with energy lower than the exciton peak of InSe at low temperature, which is attributed to Se vacancies. The work by introducing vertically aligned InSe nanoribbons provides a new strategy to manipulate the light‐matter interactions and defect engineering for novel optoelectronics, which can be also extended to other 2D semiconductors.

The subtle usage of NH4BF4: Facile and economical fabrication of Ti black surface for enhanced optical absorption performance

The Ti black surface has been widely used in aerospace and photocatalysis for many years. However, the preparation technique for the Ti black surface has several disadvantages, such as a complex process, high cost and safety concerns. In this study, a new chemical immersion method using the mixed aqueous solution of 0.715 mol/L NH4BF4 and 0.004 mol/L HF was proposed to prepare a uniform Ti black surface, which is very facile, economical and efficient. Due to the etching of HF, the light-trapping nanostructure was formed on Ti surface. Grazing incidence X-ray diffraction (GIXRD) and X-ray photoelectron spectroscopy (XPS) observations indicated that the black surface was covered by the film mainly composed of TiOx, Ti(OH)x, and TiH2. The diffuse reflectance spectra demonstrated that the black surface exhibited great optical absorption performance with the maximum reflectance of 7.6 % to the UV–visible light and 35.3 % to the near-infrared light. The as-fabricated TiOx film with narrower bandgap could be contributed to the doping of Ti3+ and F− ions. The presence of F− ions in the film prevented the Ti3+ ions in the bulk of TiOx from being oxidized. The combined contribution of light-trapping nanostructure and TiOx film enhanced the optical absorption performance of Ti surface.

Electronic and photocatalytic properties of N, V co-doped anatase TiO2

Photocatalytic technology has good stability and ecological friendliness which is used to treat organic pollutants in wastewater. In this paper, TiO2, 1.5%V–TiO2 and N, V co-doped TiO2 were synthesized by hydrothermal method for photocatalytic degradation of tetracycline. Meanwhile, XRD, HRTEM, SEM, FT-IR, XPS, UV–Vis DRS, PL and electrochemistry tests were used to characterize the catalysts. The results showed that the appropriate amount of N, V co-doped can cause structural changes of TiO2. The co-doped of N and V enhanced the photocurrent response of TiO2, increased the specific surface area, reduced the band gap, and improved the efficiency of photodegradation of tetracycline. Accordingly, the tetracycline photocatalytic degradation path was proposed. 6%N-1.5%V–TiO2 completely degraded tetracycline into CO2, H2O and NO3−. The calculation results show that an appropriate amount of N, V co-doped TiO2 decreased bandgap, improved the optical absorption performance of TiO2. This work demonstrated the potential of N, V co-doped to design efficient photocatalysts.

Photovoltaic properties of novel quaternary chalcogenides based on high-throughput screening and first-principles calculations

<sec>In recent decades, the demand for clean energy has promoted extensive research on solar cells as a key renewable energy source. Among the various emerging absorber layer materials, Kesterite-type semiconductors have aroused significant interest. Especially, Kesterite Cu<sub>2</sub>ZnSnS<sub>4 </sub>(CZTS) stands out as a promising candidate for low-cost thin-film solar cells due to its direct bandgap, high optical absorption coefficient, suitable bandgap (1.39–1.52 eV), and abundance of constituent elements. However, the power conversion efficiency (PCE) of CZTS-based solar cells currently lags behind that of Cu(In,Ga)Se<sub>2</sub> (CIGS) cells, mainly due to insufficient open-circuit voltage caused by a large number of disordered cations and defect clusters, resulting in non-radiative recombination and band-tail states.</sec><sec>To address these challenges, partial or complete cation substitution has become a viable strategy for altering the harmful defects in CZTS. This study proposes a heterovalent substitution of Zn in CZTS and explores the potential of novel quaternary chalcogenide compound <i>A</i><sub>2</sub><i>M</i><sub>2</sub><i>M'Q</i><sub>4</sub> (<i>A</i> = Na, K, Rb, Cs, In, Tl; <i>M</i> = Cu, Ag, Au; <i>M'</i> = Ti, Zr, Hf, Ge, Sn; <i>Q</i> = S, Se, Te) as absorbers for solar cells. By substituting elements in five prototype structures, a comprehensive material database comprising 1350 <i>A</i><sub>2</sub><i>M</i><sub>2</sub><i>M'Q</i><sub>4</sub> compounds is established.</sec><sec>High-throughput screening and first-principles calculations are used to evaluate the thermodynamic stabilities, band gaps, spectroscopic limited maximum efficiencies (SLMEs), and phonon dispersions of these compounds. Our research results indicate that 543 compounds exhibit thermodynamic stability (<i>E</i><sub>hull</sub> < 0.01 eV/atom), 202 compounds possess suitable band gaps (1.0–1.5 eV), and 10 compounds meet all the criteria for thermodynamic and dynamic stability, suitable band gaps, and high optical absorption performance (10<sup>4</sup>–10<sup>6</sup> cm<sup>–1</sup>), with theoretical SLME values exceeding 30%.</sec><sec>Notably, <i>Ibam</i>-Rb<sub>2</sub>Ag<sub>2</sub>GeTe<sub>4</sub> exhibits the highest SLME (31.8%) in these candidates, featuring a band gap of 1.27 eV and a small carrier effective mass (< <i>m</i><sub>0</sub>). The electronic structures and optical properties of these compounds are comparable to those of CZTS, which makes them suitable for highly efficient single-junction thin-film solar cells.</sec><sec>All the data presented in this work can be found at <ext-link ext-link-type="uri" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://www.doi.org/10.57760/sciencedb.j00213.00006">https://www.doi.org/10.57760/sciencedb.j00213.00006</ext-link>.</sec>

Enhanced photocatalytic N2 fixation and water purification using Bi/ZnSnO3 composite: Mechanistic insights and novel applications

A composite of cheap metallic Bi-decorated ZnSnO3 was synthesized via a solvothermal method and applied for photocatalytic N2 fixation for the first time. The results demonstrated that the Bi/ZnSnO3 composite with 1.5 % Bi exhibited superior photocatalytic performance. with the optimal sample producing NH3 at a rate of 988 μmol/L g-1h−1 under simulated sunlight. This is 5 times faster than that of pure ZnSnO3. Additionally, the Bi/ZnSnO3 composite showed significantly better photocatalytic performance than pure ZnSnO3 in RhB degradation. Structural analyses confirmed successful loading of Bi nanoparticles on the surface of ZnSnO3. Furthermore, diffuse reflectance spectroscopy analysis revealed that the surface plasmon resonance effect of metal Bi effectively improved the optical absorption performance. However, the sensitization of metal Bi had a limited contribution to the high photocatalytic activity of the Bi/ZnSnO3. Electrochemical analyses indicated that the Schottky barrier formed between Bi and ZnSnO3 captured photo-generated electrons and promoted the charge separation, which was considered responsible for the increased photoactivity of Bi/ZnSnO3.This work provides a new application of Bi/ZnSnO3 and may offer new ideas for the application of ZnSnO3 materials in the field of photocatalysis, which are crucial for addressing environmental pollution and energy conversion challenges.

Enhancement of photo-thermal performance using hole plasmonic nanofluids

A single nanoparticle with broadband and strong optical absorption property has great significance for expanding its utilization and saving cost in various fields. This work utilizes the near-spherical nanocavities distributed on the surface of a single nanoparticles (named as “hole nanoparticles”) to optimize the optical absorption performance and to reduce the material cost, especially for plasmonic materials. The cavity effect and the localized surface plasmon resonance effect of the hole plasmonic nanofluids can effectively regulate the absorption band to match the solar spectrum and enhance optical absorption property. Apart from gathering the incident light, the cavity effect can enhance the surface resonance effect, then further enhances the optical absorption. Based on the finite-difference time-domain method, the results show that the photothermal conversion efficiency of silver hole nanofluid and titanium nitride hole nanofluid with a cavity size of 10 nm, a cavity depth of 18 nm, and a cavity number of 49 can separately reach 89.1 % and 91 % at just 10 ppm, among which the silver hole nanofluids have higher photothermal conversion efficiency by 15.4 % than the corresponding solid nanofluids. This work provides an efficient strategy to achieve the broadband-spectrum utilization of the single nanoparticle with the low material usage.

Boosted photothermal synergistic CO2 methanation over Ru doped Ni/ZrO2 catalyst: From experimental to DFT studies

The hydrogenation of CO2 to CH4 presents a captivating and challenging avenue for CO2 reutilization. In this study, we explored the potential of photo-thermal catalytic (PTC) reactions for CO2 conversion to CH4. Herein, we employed a novel catalyst, NiRu/ZrO2, for photothermal CO2 methanation. Remarkably, the Ru-doped Ni/ZrO2 catalyst demonstrated significantly higher catalytic activity compared to the Ni monometallic catalyst. The optimized Ru doping conditions led to decreased temperature requirements and promoted CO2 conversion rates, achieving an impressive 100% CH4 selectivity. Detailed characterizations of the catalyst revealed several advantageous properties of NiRu/ZrO2, including superior optical absorption performance, a higher temperature of CO2 resolved peak, and an increased binding energy of the Ni2+ peak. Furthermore, density functional theory (DFT) calculations demonstrated that the addition of Ru positively influenced CO2 adsorption, thereby lowering the energy barrier for CO2 decomposition and C species hydrogenation. This research sheds light on the potential of the Ru-doped Ni/ZrO2 catalyst for efficient CO2 conversion to CH4 through photothermal catalysis. These findings offer valuable insights for the development of advanced catalysts in CO2 reutilization strategies.

A Rational design of Dithieno-Benzo-Dithiophene based acceptors for organic solar cells

Here, a series of Acceptor–Donor–Acceptor (A–D–A) type compounds are designed. We have theoretically investigated their structural, electronic, optical and photovoltaic properties by employing density functional theory (DFT) formalism. In this regard we have taken Dithieno[2,3−d;2/,3/−d/]benzo[1,2−b;4,5−b/]dithiophene (DTBDT) as donor unit and fused benzothiadiazole along with thiophene (spacer) and cyanoacrylic acid (CAA) (as anchoring group) as acceptor unit. We have investigated different structural and optoelectronic properties viz. dihedral angle, inter-ring bond length, bond length alternation parameters, HOMO-LUMO gap, ionization potential, electron affinity, partial density of states, reorganization energies for holes and electrons, charge transfer rate for holes and electrons, optical absorption and photovoltaic performances of all the designed molecules. Observed reorganization energy and charge transfer rate indicates the electron transporting nature of all the studied molecules. Calculated absorption properties reveal that compounds substituted with different heterocyclic rings in the donor part exhibits the higher value of absorption maximum in the visible range of electromagnetic spectrum. However, the lower values of exciton binding energy and negative Gibb’s free energy change of all the designed molecules indicate the facile charge separation at the donor/acceptor interface. Moreover, the observed photovoltaic properties indicate that all the studied compounds has potential to become candidate for application in photovoltaics. Observed theoretical power conversion efficiency (PCE) reveal that TTPy having maximum PCE of 18.44% will be the best candidate for photovoltaic applications.

Electronic and optical properties of Type-II van der Waals heterostructures X-S/ZnTe (X = Ga, Sn) under applied electric field and strain

Van der Waals Heterostructure (vdwH) has become a research hotspot due to its excellent photoelectric properties. Based on the first principles, the stability, electronic and optical properties of GaS/ZnTe vdwH and SnS2/ZnTe vdwH have been systematically investigated. The results indicate that both of them have typical Type-II band arrangement and direct band gaps of 0.56 eV and 1.39 eV, respectively, showing good stability. What is noteworthy is that the band gap of the heterostructure changes almost linearly with the increase of applied electric field intensity, and the band gap closure occurs at 0.8 V/Å and 0.9 V/Å respectively. Furthermore, the variation curve of the band gap with strain is roughly parabolic, and SnS2/ZnTe vdwH becomes metal at 6% compressive strain. Doping a Se atom in GaS/ZnTe vdwH will increase the band gap and change it into a Type-Ⅰ band arrangement. As for optics, GaS/ZnTe vdwH and SnS2/ZnTe vdwH show better optical absorption performance than monolayer in the visible region, doping, strain and electric field can make the absorption peak of heterostructure shift, and strain and electric field can improve the optical absorption coefficient. These results make clear that GaS/ZnTe vdwH and SnS2/ZnTe vdwH are good candidates for nanodevices and optoelectronic devices in the future.

Electric field combined nanofluid to enhance photothermal efficiency of the direct absorption solar collector

Compared with conventional surface absorption collectors, nanofluid-based direct absorption solar collectors (DASC) have superior optical absorption performance and photothermal conversion efficiency. However, problems such as nanoparticles deposition and large temperature difference inside the collector still limit the development of DASC systems. To solve these problems, this paper firstly proposed to apply the electric field to manipulate the motion of nanoparticles to make the upper and lower nanofluids to exchange heat in the DASC system. The Al2O3-thermal oil nanofluids with the concentration of 0.01–0.3% are prepared, and the transmittance of the nanofluids and photothermal conversion as well as mechanism are performed and analyzed. The results show that the electric field can reduce the temperature difference inside the collector and improve the photothermal conversion efficiency of the DASC system. The temperature rise and photothermal conversion efficiency of 0.2 vol% Al2O3 nanofluid at voltage of 10 kV are 62.11 °C and 87.85%, which are 19.24% and 14.17% larger than those without electric field respectively. Under the action of electric field, the resuspension of deposited nanoparticles and heat transfer between upper and lower nanoparticles work together to improve the photothermal conversion efficiency of DASC system.

Ti3C2-modified g-C3N4/MoSe2 S-scheme heterojunction with full-spectrum response effectively applied in photoreduction of CO2 to CO and CH4.

The energy shortages and global warming caused by the extensive use of fossil fuels are urgent problems to be solved at present. Photoreduction of CO2 is considered to be a feasible solution to two major global problems. The ternary composite catalyst g-C3N4/Ti3C2/MoSe2 was synthesized by hydrothermal method, and its physical and chemical properties were studied by an array of characterization and tests. In addition, the photocatalytic performance of this series of catalysts under full spectrum irradiation was also tested. It is found that the CTM-5 sample has the best photocatalytic activity, and the yields of CO and CH4 are 29.87 and 17.94 μmol g-1h-1, respectively. This can be ascribed to the favorable optical absorption performance of the composite catalyst in the full spectrum and the establishment of S-scheme charge transfer channel. The formation of heterojunctions can effectively promote charge transfer. The addition of Ti3C2 materials provides plentiful active sites for CO2 reaction, and its superior electrical conductivity is also conducive to the migration of photogenerated electrons.

Tunable electronic and optical properties of Te doped ZrS2/GaSe van der Waals heterostructures under varying electric fields and strains

Van der Waals Heterostructure (vdwH) has excellent properties due to its unique composition, which makes it leading the research craze. Based on the first principles, the geometric stability, electronic and optical properties of doped ZrS2/GaSe vdwH have been studied in detail. The results show that ZrS2/GaSe vdwH has a typical Type-II band arrangement with an indirect band gap of 0.763 eV. Doping decreases the band gap and increases the optical absorption coefficient. After the initial heterostructure is adjusted by the layer spacing or the external electric field and strain are applied, the band gap values of the heterostructure can be observed to change regularly. It is noteworthy that when positive and negative electric fields and biaxial strain are applied to the doped heterostructure, the transition from indirect to direct band gap and from Type-II to Type-I is observed. In addition, ZrS2/GaSe vdwH exhibited better optical absorption performance than monolayer in the UV region, and doping, strain and electric field all improved the optical absorption capacity of ZrS2/GaSe vdwH in the visible region.

Enhanced Open‐Circuit Voltage by Using 2,7‐Pyrene as a Central Donor Unit in A‐π‐D‐π‐A‐Type Small‐Molecule‐Based Organic Solar Cells

AbstractTo get insights into the relationship between molecular structure and performance in photovoltaic cells, two small molecules of T(3TDRCN)2 and Pr(3TDRCN)2 were synthesized with an A‐π‐D‐π‐A type backbone structure. The T(3TDRCN)2 and Pr(3TDRCN)2 were using n‐octyl side chains substituted trithiophene (3T) as the π‐linker and 2‐(1,1‐dicyanomethylene)‐rhodanine (DRCN) as terminal acceptor (A) group, while varied the central donor (D) unit from thiophene (T) to 2,7‐pyrene (Pr). Both SMs were applied as donor materials along with fullerene acceptor (PC71BM) for solution‐processed bulk‐heterojunction solar cells. The impacts of central donor units on their optical absorption, electrochemical property, hole mobility, and solar cell performance were primarily studied. The T(3TDRCN)2:PC71BM based devices yielded a power conversion efficiency (PCE) of 2.60 % with an open circuit voltage (Voc) of 0.89 V. Interestingly, the Pr(3TDRCN)2 based solar cell exhibited an higher PCE of 4.47 % with an improved Voc of 0.95 V. Our work indicates that using large π‐conjugated aromatic donor with weak‐electron donating property as central unit can improve Voc, as well as high photovoltaic efficiency of the A‐π‐D‐π‐A type SMs in organic solar cells.

The use of remote Femto Second technology in the preparation of black silicon material and optical devices.

The research aims to study the application of remote Femto Second (FS) technology in black silicon material preparation and optical devices. Based on the principle and characteristic research of FS technology, the interaction between FS and silicon is adopted to propose a scheme for preparing black silicon material through experiments. Moreover, the experimental parameters are optimized. Then, the scheme of using the FS for etching polymer optical power splitter as a new technical means is proposed. In addition, while ensuring processing accuracy, the appropriate process parameters of laser etching photoresist are obtained. The results show that the performance of black silicon prepared with SF6 as the background gas is greatly improved in the 400-2200nm range. However, the performance of black silicon samples with the two-layer structure etched at different laser energy densities has little difference. Black silicon with a Se+Si two-layer film structure has the best optical absorption performance in the infrared range of 1100nm-2200nm. Besides, the optical absorption rate is the highest when the laser scanning rate is 0.5mm/s. In the band of >1100nm, when the maximum laser energy density is 6.5kJ/m2, the overall absorption of the etched sample is the worst. The absorption rate is the best when the laser energy density is 3.9kJ/m2. It suggests that the proper parameter selection greatly impacts the quality of the final laser-etched sample.

Development of nanostructured based ZnO@WO3 photocatalyst and its photocatalytic and electrochemical properties: Degradation of Rhodamine B

The current study focused on the hydrothermal synthesis of ZnO@WO3 nanocomposite with Zn/W mole ratios of 1:1, 5:1, and 6:1, and labeled as ZnO@WO3 (1:1), ZnO@WO3 (5:1), and ZnO@WO6:1, respectively, as heterostructure photocatalyst for Rhodamine B (RhB) degradation from textile effluent. The combination of ZnO and WO3 in a short rod-like nanocomposite structure was confirmed by the structural analyses conducted using SEM and XRD. According to a study of the electrochemical properties, ZnO@WO3 can increase the lifetime of photo-generated charge carriers by having a lower charge transfer resistance and recombination rate. The optical band gaps of pure ZnO, pure WO3, and ZnO@WO3 photocatalysts were found to be 3.22 eV, 2.75 eV, and 2.42 eV, respectively, according to optical studies. Combining ZnO and WO3 semiconductor materials in a ZnO@WO3 nanocomposite can change the forbidden band width of the nanocomposite and improve optical absorption performance in the visible light region. For pure ZnO, pure WO3, and ZnO@WO3 (5:1) photocatalysts, respectively, the total treatment of 300 ml of a 10 mg/L RhB solution was achieved after 62, 75, and 55 min of visible light irradiation. The results revealed that ZnO@WO3 (5:1) demonstrated excellent photocatalytic degradation. The results showed that ZnO@WO3 (5:1) nanocomposite has effective photocatalytic degradation potential for treating RhB in real textiles.

Determining anisotropic reactive facet of ilmenite photocatalyst with Hubbard U assisted density functional theory

Findings on favorable charge-transfer pathways have been challenged for the enhancing catalytic reaction because electrical and optical efficiency are influenced by the interfacial/surface environment on the crystal structure. Herein, the electric and optical peculiarities of ATiO3 ilmenite catalyst are investigated for the anisotropic charge pathways by density functional theory framework with Hubbard U (DFT + U). The uncertainty for the best Hubbard U is simulated for the lattice parameters and band gaps in ATiO3. Our simulation corrected by Hubbard U = 10 eV shows the best reliability for ATiO3 involving 30 atoms as a basis at constant ilmenite structure and concluded that Perdew-Burke-Ernzerhof functional performance overcomes the deficiency of standard local density approximation functionals. Anisotropic carrier mobility in the Brillouin zone is compared with DFT + U on A-site cation effects. Among the representative three kinds of cations, our result shows that NiTiO3 exhibits a good optical absorption performance with the dielectric function and absorption coefficient in the visible light range, especially along the b3 direction which facilitates the separation of photogenerated electron-hole pairs at the top side of the shape. Our computational approach suggests a high reactive crystal facet of transition metal oxide contributing to the viable approach for the efficient catalytic reaction.

Construction of two-dimensional lateral heterostructures by graphenelike ZnO and GaN monolayers for potential optoelectronic applications

Constructing lateral heterostructures (LHSs) is a promising strategy to provide a new pathway to broaden the applications in nanoelectronic and nanospintronic devices. Herein, the influence of the width and strain engineering as well as vacancy defects on the electronic structures and magnetic properties of ZnO/GaN LHSs is systematically investigated by the first-principles calculations. The results show that zigzag- or armchair-(ZnO)m/(GaN)m LHSs undergo the type-I to quasi type-II band transition when the width m increases from 4 to 12. However, once m is greater than 12, zigzag LHSs exhibits metallic character. Zigzag LHSs experience a direct-to-indirect semiconducting-to-metallic transition with increasing of width m (4 ≤ m ≤ 20). The armchair-(ZnO)12/(GaN)12 LHSs with the bandgap of 1.794 eV present thermally and dynamically stable, exhibiting type-II band alignment. Moreover, armchair-(ZnO)12/(GaN)12 LHSs behaves excellent optical absorption performance in visible light range. Furthermore, a transition from type-I to quasi type-II band alignment appears in armchair-(ZnO)12/(GaN)12 LHSs when the strains are applied. Additionally, the magnetic properties of armchair-(ZnO)12/(GaN)12 LHSs can be effectively modulated by introducing vacancy defects. Armchair-(ZnO)12/(GaN)12 LHSs with VO maintains the semiconducting character, and (ZnO)12/(GaN)12 LHSs with VZn, VN and VGa exhibit semi-metallic feature with the total magnetic moments within 1∼3 μB. The current results provide vital guidance for the investigation and modulation of electronic properties of ZnO/GaN LHSs, thereby broadening the possibility of facilitating the potential applications for potential nano-optoelectronics devices.