Band Edge Alignment Research Articles

A comparative study of BiFeO3-based compounds for enhanced hydrogen evolution reaction

We present a comprehensive study, combining experimental and theoretical approaches, to assess the hydrogen evolution reaction (HER) efficiency of BiFeO3-based solid solutions. Initially, we investigate the electronic and optical properties of these compounds, with a particular focus on band edge alignment relative to water redox potentials. Our findings show that the materials exhibit optimal band gaps of approximately 2.0 eV, indicative of enhanced visible light absorption and favorable energetic alignment to drive efficient hydrogen generation. To corroborate our theoretical predictions, we perform photoelectrochemical measurements on selected BiFeO3-based compounds synthesized via the solid-state method. Our experimental results reveal a high hydrogen yield, with BiFeO3-SrTiO3 achieving a production rate of ∼114 µmol/L in 30 min, outperforming BiFeO3-BaTiO3 (∼70 µmol/L) and pristine BiFeO3 (∼61 µmol/L). These findings validate our theoretical assumptions and demonstrate the superior HER performance of BiFeO3-SrTiO3, positioning it as a highly promising candidate for sustainable hydrogen production.

Tailoring Interface via Tuning the Phase and Morphology of TiO2 for Efficient Mesoporous Perovskite Solar Cells.

The efficiency of mesoporous perovskite solar cells (mp-PSCs) is significantly influenced by favorable charge transport properties across their various interfaces. The interfaces involving compact-TiO2, mesoporous electron transport layer (ETL), and perovskite layer are particularly vital for high-performing devices. Our study presents a combined experimental and computational approach, specifically employing density functional theory, to explore the impact of mesoporous-ETL/perovskite interface properties on carrier transport. These properties are examined in relation to the phases and morphologies of the mesoporous layer. Different phases of TiO2, including anatase, rutile, and brookite, and various morphologies such as nanocubes, nanorods, and disks/clusters, were synthesized using a simple hydrothermal synthesis route. They constitute the mesoporous layer, and Cs0.05FA0.84MA0.14PbI2.55Br0.45 is used as the perovskite absorber in mp-PSCs. The performance of the resulting mesoporous-TiO2 (mp-TiO2) device was investigated in relation to the different phases and morphologies of mp-TiO2. The mp-PSCs with the anatase phase as the mesoporous ETL exhibited the highest device parameters, including power conversion efficiency of 19.15%, short-circuit current density of 22.55 mA/cm2, fill factor of 76.50%, and open-circuit voltage of 1.11 V. The superior performance of the anatase structure is attributed to its promising band edge alignment, which results from a small negative conduction band offset compared to other phases, thereby enhancing carrier transport. This study underscores the potential of interface optimization to improve device performance. By investigating the device performance across different phases and morphologies of the mp-TiO2 layer, we can pave the way for the design of next-generation energy devices.

3D/2D lead-free halide perovskite CsSnBr3/MoX (X = Se2, SSe, S2) heterostructures for high-efficiency solar cell: Interface engineering strategies and transition of band alignments

The rapid progress in the fabrication of van der Waals (vdW) heterostructures based on perovskite has significantly advanced the fields of optoelectronics and solar cells by integrating the exceptional properties of different materials. Overall, perovskite-based vdW heterostructures display unique functional characteristics due to their varied type-I, type-II, and type-III energy band configurations. However, it is a challenge to achieve flexible regulation of band edge alignment in heterostructures for different applications. Using first-principles density functional theory, we systematically study the electronic and optical properties of vdW heterostructures system consisting of three-dimensional lead-free all-inorganic halide perovskite materials CsSnBr3 and MoX (X = Se2, SSe, S2). The research results show that in the CsSnBr3/MoX vdW heterostructures, type I, II, and III transitions of band arrangements are achieved through interface engineering strategy to adapt to different applications. Meanwhile, by calculating the light absorption efficiency of the constructed 3D/2D vdW heterostructures, it was found that the interface effect enhances the optical absorption range and intensity of the perovskite-based heterostructures. The theoretically estimated power conversion efficiency (PCE) of the heterostructure thin-film solar cell reaches 21.4 %. The results of our research indicate that the controllable band alignment of CsSnBr3/MoX heterostructures has significant potential for future applications in optoelectronics.

A new type of pentagonal structure HgS2 monolayer with abundant active sites and low Gibbs free energy for photocatalytic water splitting

Discovery of new two-dimensional (2D) materials not only has important fundamental research significance but also has promising application prospects. Through systematic structure searching combined with density functional theory calculations and simulations, we predict a new 2D monolayer HgS2 material featuring with a previously unreported type of pentagonal structure with orthorhombic P21212 symmetry. The penta-HgS2 monolayer shows good thermal, thermodynamic, mechanical and dynamic stabilities, exhibiting ferroelastic phase transition with an ultralow switching energy barrier (about 1 meV/atom), high ultimate strength of 12 N/m, moderate indirect band gap of 2.25 eV. In addition, the penta-HgS2 monolayer shows significantly anisotropic carrier mobility with a large anisotropy ratio of 98.5 along the y direction. More importantly, the penta-HgS2 monolayer exhibits abundant catalytic active sites, low Gibbs free energy (ΔGH ranging from 0.656 to 1.687 eV) for hydrogen evolution reactions, excellent solar light absorption capacity (∼105 cm−1) with the solar-to-hydrogen efficiency reaching up to 11.83%. The excellent ultimate tensile ability and the ultralow ferroelastic phase transition energy barrier implies penta-HgS2 monolayer material can be used to manufacture flexible mechanical and nanoelectronic devices. The suitable band edge alignments, ultrahigh carrier mobility anisotropy, high catalytic activity and excellent visible light adsorption performance indicate that penta-HgS2 monolayer is a promising candidate photocatalyst for high-performance photocatalytic water splitting. The present work not only supplements a new member to the 2D pentagonal structure material family, but also points out its promising applications in nanoscale devices and photocatalytic hydrogen productions.

Dimensionality and strain-dependent properties of Orthorhombic (100) NaTaO3 thin films: A comprehensive DFT investigation

The modulation of perovskite oxide thin films’ properties, through both intrinsic and extrinsic methods, has been extensively studied to enhance their photocatalytic performance. We employed ab initio density functional theory calculations to investigate the layer-dependent structural and electronic properties of orthorhombic NaTaO3 thin films. Our findings reveal that slabs comprising five, four, and three layers retain the non-magnetic and semiconducting characteristics of the bulk material, with their properties progressively converging towards those of an infinite-surface slab as the number of layers increases. Biaxial in-plane strain induces a linear change in the structure of surface TaO4 tetrahedra, thereby altering the film’s band gap. Notably, the two-layer slab exhibits a transitional behavior between the bulk-like nature of thicker films and the unique features of a NaTaO3 monolayer, showing heightened sensitivity to strain. Under compression, this bilayered system acquires bulk-like properties, whereas its strain-free state is magnetic and metallic akin to the monolayer. Similar transitions are observed in the latter, though under higher compression values. We provide an in-depth discussion of the structural and electronic mechanisms underlying these transitions. Additionally, the relative band-edge alignment with water-splitting photocatalytic potentials underscores the complex interplay between strain and dimensionality. This work offers valuable insights towards the design of more efficient photocatalysts, highlighting the potential of engineered NaTaO3 thin-film structures for advancing photocatalytic applications.

Two-dimensional ferroelastic semiconductors InXY (X = S, Se; Y = Cl, Br, I): Promising candidates for photocatalytic water splitting with tunable electronic anisotropy

We have identified a class of two-dimensional ferroelastic monolayers, denoted as InXY (where X = S, Se; Y = Cl, Br, I), through first-principles calculations. The dynamic, thermal, and mechanical stabilities of these InXY monolayers are validated by phonon dispersion spectra, AIMD calculations, and elastic constants, respectively. These monolayers exhibit semiconducting behavior with bandgaps ranging from 1.94 to 2.85 eV and possess excellent ferroelasticity with strong ferroelastic signals and moderate ferroelastic switching barriers. Notably, the band edge positions of InSBr and InSI monolayers are observed to stride the water redox potentials at pH = 0, indicating their potential as photocatalysts for water splitting in acidic environments. We also explored the effects of biaxial strain on the band edge alignments and photocatalytic performance of these monolayers. Moreover, the InXY monolayers exhibit excellent anisotropic optical absorption across the visible to ultraviolet regions, along with high anisotropic carrier transport. The coupling of ferroelastic and anisotropic properties in these monolayers offers promising opportunities for designing controllable electronic devices, thereby expanding their potential applications in multifunctional materials. Our findings reveal that the InXY monolayers are promising candidates for efficient photocatalytic water splitting and controllable optoelectronic applications.

Triangle CeO2/g-C3N4 heterojunctions: Enhanced light-driven photocatalytic degradation of methylparaben

In this work, an efficient photocatalytic system for methylparaben (MP) removal, using solar (λ > 360 nm) and visible (λ > 420 nm) light-driven CeO2/g-C3N4 (CeO2/CN) heterojunctions is reported for the first time. The physicochemical properties of pure CeO2, CN, and CeO2/CN composites were investigated using characterization techniques, such as XRD, FESEM-EDS, TEM, UV–Vis, PL, XPS, and electrochemical spectroscopy. Among the catalysts with different mass ratios of CeO2, 10 %CeO2/CN showed the best photocatalytic performance. This is attributed to the enhanced charge carrier’s separation because of the proper band-edge alignment between CN and CeO2 components, and the strong visible light absorbance. The photocatalytic degradation of MP followed the first-order kinetics, and the 10 %CeO2/CN catalyst exhibited a 3.8- and 11.3-times higher reaction rate (k) constant than that of pure CN, investigated under solar and visible light illumination, respectively. Further, scavenger trapping experiments confirmed that hydroxyl radicals (OH.) and dissolved oxygen are the predominant active species in MP oxidation over 10 %CeO2/CN composite catalyst. 1H NMR and LCMS-HPLC results and observations showed complete degradation of MP (0.1 g/L) to CO2 and H2O after 7 h of solar irradiation, due to the absence of the representative peaks of MP and its organic degradation products (e.g. phenols, benzoates).

A new CsPbI2Br/CuZnSnSSe/Si tandem solar cell with higher than 32 % efficiency

To avoid Shockley-Queisser limit in single p-n junctions, tandem solar cells were proposed. A new tandem cell is simulated here using the 1-dimensional SCAPS. The new cell combines two reported single solar cells together, aiming at achieving high performance by optimizing various layer characteristics. The bottom sub-cell is Mo/Si(p)/CZTSSe(p)/CdS(n)/ZnO(i)/ZnO(Al), where ZnO is an electrodeposited transparent-conductor oxide, with high UV transmittance, ZnO(i) is intrinsic layer, CZTSSe/Si is bi-absorber layer of p-CuZnSnSSe and p-Si, Mo is back contact. The optimized sub-cell exhibits a high fill factor of 85.18 % with overall efficiency 20 %. Based on literature, a perovskite CsPbI2Br layer is included in the top sub-cell Cu2O(HTL)/CsPbI2Br)/TiO2(ETL), where Cu2O is a hole-transport layer and TiO2 is electron-transport layer. The top sub-cell layers have been carefully selected for best alignment. Matching and optimizing various parameters in the two sub-cells is a simulation challenge. Therefore, layers in the two sub-cells have been studied separately, keeping in mind the proper combinations between various layers. With optimized layer thicknesses and band gaps, together with proper alignment of band edges, the proposed tandem solar cell exhibits high characteristics of 80 % fill factor and higher than 32 % overall efficiency.

Electronic and optical properties of COFs/graphene and COF/hBN heterostructures

Covalent organic frameworks (COFs) are a class of intriguing materials with tunable electronic and optical properties. In this work, we investigate the electronic and optical properties of COFs embedded with hBN and graphene. Our results demonstrate that graphene integration enhances the ultraviolet and visible light absorption of C6N6 and B6O6 monolayers, while charge transfer in all COF/graphene heterostructures leads to the formation of a built-in electric field. Furthermore, we show that incorporating hBN into B6O6 and C6N6 heterostructures enables control of their bandgap through an applied electric field, resulting in a semiconductor-to-metal transition under moderate electric field strengths. Additionally, B6O6/hBN exhibits suitable band edge alignment for photocatalytic water splitting. These findings provide valuable insights into the electronic and optical properties of COF heterostructures and their potential applications in electronic and optoelectronic devices. Our study contributes to ongoing efforts in the design and development of novel COF and 2D material heterostructures for future electronic and photonic applications.

A novel and promising Penta-Octa-Based silicon carbide semiconductor

Penta-octa-graphene (POG) consists of pentagonal and octagonal carbon rings, hosting type-I and type-II Dirac line nodes due to its sp2 and sp3 mixed bonds. Inorganic analogs of 2D carbon lattices have increased the potential applications and changed the main properties of carbon-based structures. Therefore, this work proposes penta-octa-graphene based on silicon carbide using DFT simulations. With a cohesive energy of −5.22 eV/atom, POG-Si5C4 is energetically viable in comparison with other silicon carbide-based monolayers. Phonon dispersion analysis confirms the POG-Si5C4 dynamical stability. MD simulations demonstrate that this new monolayer can withstand temperatures up to 1020 K. Electronic analysis indicates it is a semiconductor with an indirect band gap transition of 2.02 eV. The mechanical properties exhibit anisotropy, with Young’s modulus ranging from 38.65 to 99.47 N/m and an unusual negative Poisson’s ratio of −0.09. The band edge alignment suggests that POG-Si5C4 holds potential for hydrogen generation through photocatalytic water splitting. This research opens possibilities for designing inorganic penta-octa-based structures and provides insights for future experimental and theoretical studies focused on exploring and optimizing advanced silicon-carbide 2D materials.

Reversing Internal Electric Field Direction at BiVO4/TiO2 Heterostructure Interface by a Thin W‐VO2 Layer: Turning Waste Charge Carriers into Wealth

AbstractIn heterojunction photocatalysts, the band edge alignment and internal electric field (IEF) direction significantly affect the charge carrier separation, thus the photoconversion efficiency. For example, because of an unfavorable band alignment and compared to BiVO4 alone, BiVO4/TiO2 results in ≈24% reduction in photocurrent density in this study. Herein, a tungsten‐doped VO2 (W‐VO2) thin film is inserted between BiVO4 and TiO2 to modify unfavorable spike‐like conduction band offset and IEF direction in ternary heterojunction. After reversing the IEF direction and engineering the band edges through W‐VO2 insertion, the photocurrent density is enhanced by ≈145% and ≈91% compared to BiVO4/TiO2 and BiVO4, respectively at 1.23 V versus RHE. Besides, under visible light irradiation, the kinetics rate constant for tetracycline removal by BiVO4/W‐VO2/TiO2 photocatalyst is 225% higher than that of BiVO4/TiO2, due to utilizing charge carriers before being recombined, without doping the BiVO4 and TiO2 structures. Lastly, LC‐HR‐MS/MS analysis followed by the Toxicity Estimation Software Tool (T.E.S.T.) reveals the high importance of the band alignment on the detoxification of the solution. The tunability of the VO2 work function with a low bandgap, yet distinctive valence and conduction bands (which distinguished it from metals) opens new avenues for designing high‐performance heterojunction‐based devices.

Robust type-III C3N/Ga2O3 van der Waals heterostructures

By combining two-dimensional (2D) materials with different band alignments at the contact interface, van der Waals heterostructures (vdWHs) can achieve multifunctional device applications. Here, through first principles methods, we constructed two C3N/Ga2O3 vdWHs named P↑ and P↓ because of the intrinsic polarization of Ga2O3 to study electronic, interfacial and optical characteristics. We find that the P↑ and P↓ both display a unique kind of band alignment known as broken-gap or type-III. This feature makes them highly suitable for tunnel field effect transistors (TFETs) applications. To the best of our knowledge, the tunnel window of the P↓ is the largest among the theoretical studies, reaching 0.993 eV. The electronic structure and band edge alignment of the C3N/Ga2O3 vdWHs show a weak dependence on strain engineering or external electric field. Normal-to-plane compressive strains effectively enhance the tunneling probability. We can acquire essential insights into this novel material system and its promise for future TFETs by analyzing the electrical characteristics of the C3N/Ga2O3 vdWHs.

A direct Z-scheme photocatalyst PtS2/HfGe2N4 van der Waals heterostructure for highly efficient water splitting: first-principles study

The PtS2/HfGe2N4 heterojunction features a type-II band alignment and operates as a direct Z-scheme photocatalyst. The band edge alignment is well-suited for photocatalytic water splitting.

Wide-direct-band-gap monolayer carbon nitride CN2: a potential metal-free photocatalyst for overall water splitting.

Two dimensional metal-free semiconductors with high work function have attracted extensive research interest in the field of photocatalytic water splitting. Herein, we have proposed a kind of highly stable monolayer carbon nitride CN2 with an anisotropic structure based on first principles density functional theory. The calculations of electronic structure properties, performed using the HSE06 functional, indicate that monolayer CN2 has a wide direct band gap of 2.836 eV and a high work function of 6.54 eV. And the suitable band edge alignment, high electron mobility (∼103 cm2 V-1 s-1) and visible-light optical absorption suggest that monolayer CN2 has potential on visible-light photocatalytic water splitting at pH ranging from 0 to 14. Moreover, we have observed that uniaxial strain can effectively control the electronic structure properties and optical absorption of monolayer CN2, which can further improve its solar to hydrogen efficiency from 9.6% to 16.02% under 5% uniaxial tension strain along the Y direction. Our calculations have not only proposed a new type of potential metal-free photocatalyst for water splitting but also provided a functional part with high work function for type-I and scheme-Z heterojunction applied in photocatalytic water splitting.

Interlayer angle dependence of photoelectric properties of Sb/SnC van der Waals heterojunction and its application*

The discovery of novel properties in twisted bilayer graphene has opened up new avenues of research in physics and materials science, making the twistronics a new research hotspot. In this paper, based on two-dimensional tin-based materials and antimonene monolayers, six types of Sb/SnC two-dimensional van der Waals heterostructures (vdWH) with different interlayer twist angles are constructed, and their optoelectronic properties and applications are studied by first-principles calculations. All modeling and calculations are performed using the density functional theory (DFT) software Quantum-ATK. The results show that the Sb/SnC vdWHs with six different interlayer twist angles have various band gaps, and when the interlayer twist angles are 10.89°, 19.11°, 23.41°, and 30°, the Sb/SnC vdWH exhibit a type-I band edge alignment, while at 8.95° and 13.59°, they present a type-II band structure. The results of the orbital-projected band structures of the Sb/SnC vdWHs reveal that the variation in interlayer twist angles changes the atomic stacking in the heterostructures, thereby modifying orbital coupling and further tuning the electronic structure of the heterostructures. Additionally, the calculated absorption spectra indicate that comparing individual Sb and SnC monolayers with Sb/SnC vdWHs, the latter’s absorption coefficient r is significantly enhanced in the visible light region, and the optical absorption characteristics of the heterostructures with different interlayer twist angles vary markedly. In terms of applications, as materials for solar cells, the Sb/SnC vdWHs with interlayer twist angles of 8.95° and 13.59° exhibit photovoltaic conversion efficiencies of 17.48% and 18.59%, respectively; as photocatalysts for the complete water splitting, the Sb/SnC vdWH with an interlayer twist angle of 8.95° can catalytically decompose water across a pH range of 0–2, while a twist angle of 13.59° confines its catalytic activity to a pH value between 0 and 1. Therefore, Sb/SnC van der Waals heterostructures have special rotation angles and have multifunctional application prospects in the fields of solar energy and photocatalysis. More importantly, our research demonstrates that in addition to traditional methods such as strain, doping, and defects, adjusting the interlayer twist angle provides a new degree of freedom for manipulating the optoelectronic properties of materials.

Rational design of 2D Janus P3m1 M2N3 (M = Cu, Zr, and Hf) and their surface-functionalized derivatives: ferromagnetic, piezoelectric, and photocatalytic properties.

In this study, first-principles calculations were employed to rationally design two-dimensional (2D) Janus transition metal nitrides of P3m1 M2N3 phases, where M is a d-block element (Sc-Zn, Y-Cd, Hf-Hg). Among the 29 examined 2D M2N3, three 2D phases, namely P3m1 Cu2N3, Zr2N3, and Hf2N3, exhibit excellent thermodynamic, dynamic, mechanical, and thermal stabilities. These novel Janus 2D materials exhibit ferromagnetic metallic and half-metallic behavior. The related 2D Janus surface-functionalized derivatives, Cu2N3H, Cu2N3F, Cu2N3Cl, Zr2N3H, Hf2N3H, and Hf2N3F, are all dynamically stable. The 2D Janus P3m1 phases of Zr2N3H, Hf2N3H, and Hf2N3F, all with M in the +IV oxidation state, act as semiconductors in the visible region, with energy band gaps of 2.26-2.70 eV at the HSE06 level of theory. On the other hand, the 2D Janus P3m1 Cu2N3X phases (where X = H, F, and Cl) are ferromagnetic half-metals. Additionally, it has been unveiled that there are high hole mobilities (∼6 × 103 cm2 V-1 s-1) derived from the moderate deformation potential and effective mass in the 2D Janus P3m1 Zr2N3H, Hf2N3H, and Hf2N3F phases. Uniaxial strain engineering has demonstrated the outstanding in-plane piezoelectric properties of 2D Janus P3m1 Zr2N3H, Hf2N3H, and Hf2N3F with high d11 values (∼99.91 pm V-1). Furthermore, the desirable band-edge alignments and high anisotropic carrier mobilities of 2D Janus P3m1 Zr2N3H, Hf2N3H, and Hf2N3F phases indicate their potential as visible light-driven photocatalysts for water splitting reactions on different facets. These properties render 2D Janus P3m1 Zr2N3H, Hf2N3H, and Hf2N3F phases promising for use in optoelectronics, piezoelectric sensing, and photocatalysis applications.

High stability and tunable hydrogen evolution material with defect-enhanced photocatalytic properties:penta-BAs5 monolayer

In this work, on the basis of first principles calculations, we theoretically predict a pentagonal structure material called penta-BAs5 and discuss the photocatalytic properties under its intrinsic and defective modes. Formation energy and phonon dispersion curve all proved its high stability. Penta-BAs5 has a 2.38 eV bandgap and has indirect bandgap semiconductor performance. Surprisingly, by analyzing the band edge distribution, the Gibbs free energy changes (ΔG), and applying strain, it is found that penta-BAs5 can spontaneously proceed the hydrogen evolution reaction (HER) can under neutral and acidic conditions. Interestingly, after applying electric field in the range of 0–0.8 eV/Å, the band edge alignment can keep stable. Intriguingly, the hydrogen evolution capacity of penta-BAs5 was greatly improved when the defects were present. Our study predicted a new two-dimensional pentagonal binary compound, broadened the field of the pentagonal structure families, and identified its application prospects in photocatalysis.

First principles study of the role of C in tuning the band gap of Al, Si-doped SrTiO3 to enhance photocatalytic activity

This work demonstrates that C-assisted Al, Si-doping can effectively regulate the band structure of SrTiO3 for improving photocatalytic activity. The effects of (Al + C) and (Si + C) co-doping on electronic structure and optical properties of SrTiO3 are performed by first-principles calculations. It is found that the auxiliary effect of the C element on the two doped systems is different. The (Al + C) co-doping effectively passivates the impurity band in the Al mono-doping case, which leads to the expansion of the band gap. On the contrary, the (Si + C) co-doping induces an impurity band near the top of the valence band and narrows the gap, which is ascribed to the strong coupling between C and O atoms. The calculated light absorption curves imply that (Al + C) and (Si + C) co-doping are effective ways to expand the light response region. The further analysis of band edge alignments of both the two co-doped systems indicates that (Si + C) co-doped SrTiO3 is more favorable for water splitting.

An in-depth photoluminescence investigation of charge carrier transport in ZrO2|V2O5 type I junction: Probing the production of hydroxyl radicals

The determination of the band edge positions turns out to be of particular importance in different fields. We present a comparison of different approaches for the determination of the band edge alignment. For this purpose, we suggested studying the ZrO2|V2O5 heterojunction. The structural properties investigated by means of X-ray diffraction (XRD) revealed the formation of pure V2O5 with an orthorhombic structure. The resulting ZrO2, however, exhibits two different phases (monoclinic and tetragonal). Based on the absorption spectra, the near-band edges for V2O5, ZrO2, and ZrO2|V2O5 were found to be 2.07, 4.9, and 2.12 eV, respectively. The corresponding band gap values determined by the Tauc method were found to be 2.32, 5.16, and 2.35 eV, respectively. The down-conversion photoluminescence (PL) spectra of pure and junctioned materials are discussed in detail. The up-conversion in ZrO2 revealed its band gap value (∼5.14 eV), which is very close to the one obtained by the Tauc method (∼5.16 eV). The band gap alignment of the ZrO2|V2O5 heterojunction was determined using Sanderson method and experimentally using X-ray photoelectron spectroscopy (XPS). In this work, we propose an In-depth photoluminescence study for the confirmation of the type of heterojunction by probing the hydroxyl radical (HO•) production.

Effect of codoping of rare earth elements and Cr on multiferroic, optical and photocatalytic properties of BiFeO3

In the present work, first principle calculations have been performed to study the combined effect of A (Bi) and B (Fe) site doping on the structural, multiferroic, optical and photocatalytic properties of BiFeO3 (BFO). Rare earth elements (La, Ce, Gd, Nd, Er and Eu) are doped at the A-site while Cr is doped at the B-site in perovskite BFO. A variation in total magnetic moments and spontaneous polarization of the doped systems is observed that are governed by the introduction of the rare earth elements. A maximum polarization of 110μC/cm2 is obtained for (Gd,Cr) doped BFO and the maximum magnetization of 5.1μB/cell is obtained for (Nd,Cr) doped BFO. From the study of partial electronic density of states it has been observed that amongst all the dopants incorporated as rare earth elements, the (Er,Cr)BFO system exhibits the minimum bandgap of 1.94 eV and thus shifts the absorption edge deep into the visible region which has been confirmed through the optical spectra. The band-edge alignment of the pure and codoped systems has revealed that (Er,Cr)BFO exhibits the maximum potential to be a promising photocatalyst with improved efficiency as compared to pristine BFO.