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Band edge positions of In 2 Se 3 monolayer, MoS 2 monolayer and In 2 Se 3 /MoS 2 heterostructure with respect to vacuum level based on HSE06 calculation.
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Two-dimensional photocatalyst with full-optical absorption has attracted widespread interests for water splitting and pollutant degradation. While few single materials have achieved without any regulation. In this work, we design a layered In2Se3/MoS2 heterostructures firstly in theory and demonstrate its great oxidation capacity that can be applie...
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... Nevertheless, a material of excellent oxidation ability can split water or degrade pollutants with the use of a sacrificial agent or when used as a photoanode. To illustrate the oxidation ability of In 2 Se 3 /MoS 2 , we studied the band edge alignment of the monolayers and heterostructure with respect to the redox potential of water using HSE06 (Fig. 6). The CBM and VBM of the In 2 Se 3 monolayer were −5.11 eV and −6.60 eV, while those of the MoS 2 monolayer were −4.21 eV and −6.33 eV, respectively. The results revealed that the In 2 Se 3 monolayer is capable of O 2 oxidation but not H 2 reduction, while the MoS 2 monolayer is capable of full water splitting. Regarding the In 2 Se 3 ...
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Citations
... 7 Recently, theoretical calculations and experiments have shown that emerging 2D a-In 2 Se 3 can form spontaneous ferroelectric polarization owing to its special dissymmetric structure, which is regarded as a promising photocatalytic water splitting material. [8][9][10] The 2D g-C 3 N 4 plays an increasingly significant role in photocatalysis, but the high recombination rate of photogenerated carriers significantly limits the efficiency of the g-C 3 N 4 photocatalyst. [11][12][13][14][15] To overcome the limitations of g-C 3 N 4 , various pivotal strategies have been explored, including morphology modulation, element doping, and heterostructure construction. ...
Ferroelectric materials with internal spontaneous polarization are conducive to enhancing photocatalytic performance by promoting photogenerated carriers separation. However, the traditional perovskite-type ferroelectric photocatalysts possess a typical 3D structure that is constrained by few exposed catalytic active sites and low specific surface area when compared to a 2D structure. In our study, the electronic properties of the 2D ferroelectric heterostructure for carbon and oxygen co-doping g-C3N4 (COCN)/In2Se3 with different out-of-plane ferroelectric polarization directions are investigated by first-principle calculations, namely, COCN/DOWN and COCN/UP heterostructures. The results show that when the ferroelectric polarization of the 2D In2Se3 layer in heterostructures is reversed, the heterostructure switches from traditional type-II (COCN/DOWN heterostructure) with an indirect bandgap of 1.58 eV to S-scheme (COCN/UP heterostructure) with a direct bandgap of 1.43 eV, in which the band edge positions of the S-scheme COCN/UP heterostructure satisfy the redox potential of the efficient photocatalytic selective oxidation of toluene to benzaldehyde. Further investigations revealed that the application of an electric field 0 ∼ +0.3 V/Å can reduce the bandgap and enhance the out-of-plane polarization of the COCN/UP heterostructure, which improve the photocatalytic activity of the S-scheme COCN/UP heterostructure. This work highlights the significance of ferroelectric polarization for charge transfer in heterostructures and provides theoretical guidance for the design of high-performance S-scheme photocatalysts.
... The optimized lattice parameters are a = b = 3.845 Å for the ZnIn 2 S 4 monolayer and a = b = 3.993 Å for the α-In 2 Se 3 monolayer. They are in good agreement with the previous experimental data (a = b = 3.850 Å for the ZnIn 2 S 4 monolayer, and a = b = 4.026 Å for the α-In 2 Se 3 monolayer), 13,24,37,38 which indicated that our calculations are reasonable and reliable. In order to study the thermodynamic stability of structure, AIMD simulations of the ZnIn 2 S 4 monolayer and the α-In 2 Se 3 monolayer with a time of 10 ps are carried out at finite temperatures. ...
It is of great significance to design an efficient heterostructure for photocatalytic hydrogen production to solve the energy shortage and environmental crisis. In this letter, we investigate the structure, electron of interface, optical, charge transfer, and photocatalytic mechanism of three different ZnIn 2 S 4 /α-In 2 Se 3 heterostructures by hybrid density functional calculation. It is interesting that the presence of an external electric field not only can change the bandgap but also can modulate the band alignment type. Among them, heterostructure A belongs to type II heterostructure, and heterostructure B and C belong to a Z-scheme heterostructure. Especially in heterostructure C, the electrons deposited on CBM of a ZnIn 2 S 4 monolayer will play an important role in the hydrogen production process. Meanwhile, the small bandgap of ZnIn 2 S 4 /α-In 2 Se 3 Z-scheme heterostructures enables it to obtain a wide light absorption range. Therefore, this study contributes to the design of a novel and potential Z-scheme heterostructure photocatalyst with broad application prospects in both electronic and optoelectronic fields.
... In this work, the calculations are performed by density function theory with the projector augmented plane-wave method [21] and the generalized gradient approximation of the Perdew-Burke-Ernzerhof (PBE) functional through the vienna ab initio simulation package [22][23][24][25][26]. A plane-wave cutoff energy of 300 eV is employed in all calculations. ...
Recently, the effect of dimensional control on the optoelectronic performance of two-dimensional (2D)/three-dimensional (3D) single perovskites has been confirmed. However, how the dimensional change affects the photoelectric properties of 2D/3D all-inorganic double perovskites remains unclear. In this study, we present a detailed theoretical research on a comparison between the optoelectronic properties of 3D all-inorganic double perovskite Cs2AgBiBr6 and recently reported 2D all-inorganic double perovskite Cs4AgBiBr8 with Ruddlesden-Popper structure based on density functional theory calculations. The results demonstrate the charge carrier mobility and absorption coefficients in the visible spectrum of Cs4AgBiBr8 (2D) is poorer than Cs2AgBiBr6 (3D). Moreover, the value of exciton-binding energy for 2D RP all-inorganic double perovskite Cs4AgBiBr8 (720 meV) is 3 times larger than that of 3D all-inorganic double perovskite Cs2AgBiBr6 (240 meV). Our works indicate that Cs4AgBiBr8 (2D) is a promising material for luminescent device, while Cs2AgBiBr6 (3D) may be suitable for photovoltaic applications. This study provides a theoretical guidance for the understanding of 2D RP all-inorganic double perovskite with potential applications in photoluminescent devices.
... It can thus be suggested that the interfacial contact between In 2 Se 3 and Cs 2 SnI 2 Cl 2 belong to weak van der Waals (vdW) contact, and In 2 Se 3 /Cs 2 SnI 2 Cl 2 heterostructures can preserve the excellent electronic properties of the In 2 Se 3 and Cs 2 SnI 2 Cl 2 monolayers. [33][34][35][36][37][38][39][40][41][42][43][44] In addition, considering the different descriptive mechanism for ferroelectric polarization provided by the local density approximation (LDA) and generalized gradient approximation (GGA), we supplemented the band structure calculation of In 2 Se 3 /Cs 2 SnI 2 Cl 2 heterostructure for different polarization directions by using LDA method, the results are set out in Fig. S5. Data from this figure can be compared to the data in Figs. ...
Ferroelectricity is an important source of the fascinating optoelectronic properties of heterostructures. Interfaces formed between ferroelectrics and oxides or transition metal dichalcogenides have undergone rapid development. However, the integration of ferroelectrics and two-dimensional Ruddlesden–Popper (RP) perovskites has rarely been studied so far. Herein, we use first-principle calculations to investigate ferroelectric polarization and electric field control of band alignments within the RP perovskite-based heterostructure α-In2Se3/Cs2SnI2Cl2. Our calculations demonstrate that the band alignment of heterostructure can be changed from type-II to type-III by switching the ferroelectric polarization direction in the α-In2Se3 layer. Furthermore, application of an external electric field can modulate the band structure of the α-In2Se3/Cs2SnI2Cl2 heterostructure and induce the band alignment transition. These findings highlight the importance of ferroelectric polarization switching in band alignment engineering and suggest the possibility of electric field-tunable multi-band alignment in Ruddlesden–Popper perovskite-based heterostructures.
... Figure 1(a) shows the initial geometric structure of Cs 2 PbI 2 Cl 2 /Pd 2 Se 3 heterostructure. We calculated the binding energy (E b ) of Cs 2 PbI 2 Cl 2 /Pd 2 Se 3 heterostructure as a function of interlayer separation d by the equation [43][44][45]: ...
Perovskite-based van der Waals heterostructures with high carrier mobility and perfect photoresponse performance can be used to design transistors and photovoltaic devices. However, the function of a single heterojunction is relatively limited because of its specific energy band type. To achieve more controllable device functions, in this work, the band structure, effective mass, optical absorption spectrum, differential charge density and other electronic and optical properties for the novel heterostructure system composed of emerging two-dimensional material Pd2Se3 with a high electron mobility and all-inorganic halide perovskite Cs2PbI2(1+x)Cl2(1-x) is systematically studied by using density functional theory. The results demonstrate that the band alignments in Cs2PbI2Cl2/Pd2Se3 heterostructure realize the transition from type-I to type-II by changing the concentration of I and Cl atoms in the all-inorganic two-dimensional Ruddlesen-Popper perovskite Cs2PbI2Cl2, which can be applied to different functional devices. With the increase of iodine atoms, the valence band maximum (VBM) contributed by Pd2Se3 in the heterostructure moves downward, and the valence band of Cs2PbI2Cl2 becomes the new VBM. Moreover, the transport and optical properties for the Cs2PbI2Cl2/Pd2Se3 heterostructure can be improved, due to the reductions in the band gap and effective mass, which are caused by the transition of band alignment. Our works indicate that a controllable band alignment of Cs2PbI2Cl2/Pd2Se3 heterostructure can provide theoretical guidance for the flexible designs of devices with multi-functional applications.
In recent years, α-In2Se3 has attracted great attention in miniaturizing nonvolatile random memory devices because of its room temperature ferroelectricity and atomic thickness. In this work, we construct two-dimensional (2D)...
In this work, the effect of 10 MeV electron irradiation on the structure and electrical properties of bulk α-In2Se3 crystals is studied by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray microanalysis, atomic-force microscopy, and Raman spectroscopy methods. Droplets of 200-500 nm in size were detected on the bulk α-In2Se3 crystal surface. The droplets can be formations with the γ-In2Se3 crystalline phase. The current-voltage characteristics measured by conductive atomic-force microscopy are different on and outside the droplets after electron irradiation. On the droplets, slightly better conductive properties were detected after irradiation with the electron fluence of 1015 cm-2. It is found that local resistance increases significantly for both on and outside the droplets after irradiation with the electron fluence of 1017 cm-2. Our study shows that electron irradiation can contribute to the disappearance of ferroelectric domains in the bulk α-In2Se3 crystals. Also, the distribution of surface potentials measured by Kelvin probe force microscopy becomes more uniform after electron irradiation. The results obtained in the work allow us to calculate the operating time of the device containing α-In2Se3 under conditions of long-term electron irradiation with high-energy electrons. The study shows that α-In2Se3 is a very promising material for applications in the aerospace and nuclear industries.
