Enhanced visible-light-driven photocatalytic activity in SiPGaS/arsenene-based van der Waals heterostructures.

Van der Waals heterostructures (vdWHs) showcase robust and tunable light-matter interactions, establishing an intriguing realm for investigating atomic-scale photocatalytic properties. Here, we employ ab initio methods to study the photocatalytic and optical properties of semiconducting SiPGaS/arsenene-based vdWHs with a type-II band alignment. Across the heterointerfaces, there exists significant built-in electric fields and large potential drop, in turn facilitating the spatial separation of photo-generated electron-hole pairs. These vdWHs further possess high carrier mobility in the order of 102 cm2V⁻1S⁻1, which combining with appropriate band edge positions, endow the vdWHs an absorption coefficient of ∼105 cm⁻1 to harvest a maximal portion of the solar spectrum for visible-light-driven photocatalytic applications. Our findings also reveal transition of the type-II band alignment in a type-III configuration via compressive strain for tunneling field-effect transistor application. Furthermore, both types of vdWHs exhibit enhanced suitability for photocatalysis under conditions with a pH of 2.

High thermoelectric performance of two-dimensional SiPGaS/As heterostructures.

Thermoelectric technology holds great promise as a green and sustainable energy solution, generating electric power directly from waste heat. Herein, we investigate the thermoelectric properties of SiPGaS/As van der Waals heterostructures by using computations based on density functional theory and semiclassical Boltzmann transport theory. Our results show that both models of SiPGaS/As van der Waals heterostructures have low lattice thermal conductivity at room temperature (300 K). Applying 4% tensile strain to the models leads to a significant enhancement in the figure of merit (ZT), with model-I and model-II exhibiting ZT improvements of up to 24.5% and 14.8%, respectively. Notably, model-II outperforms all previously reported heterostructures in terms of ZT value. Additionally, we find that the maximum thermoelectric conversion efficiency (η) for model-II at 4% tensile strain reaches 23.98% at 700 K. Our predicted ZTavg > 1 suggests that these materials have practical potential for thermoelectric applications over a wide temperature range. Overall, our findings offer valuable insights for designing better thermoelectric materials.

The versatile characteristics of Ars/SGaInS van der Waals heterostructures.

Two-dimensional (2D) materials with upright stacking form layered van der Waals heterostructures (vdWHs) are currently believed to be attractive prospects for optoelectronic, photocatalytic, and thermoelectric devices because they can merge the capabilities of distinct 2D materials. Herein, we evaluate the electronic, optical, photocatalytic, and thermoelectric response of model-I and model-II of Ars/SGaInS vdWHs via first-principles computations. The energetic, dynamical, and thermal stabilities of these vdWHs suggest great promise in experimental functionality. Model-I and model-II are indirect semiconductors with type-II band alignment and bandgaps of 1.53 eV and 1.86 eV, respectively. The built-in electric field considerably accelerates the transmission of electrons from the Ars layer to the SGaInS layer. Compared to pristine monolayers, both models contain appropriate band edge positions to ensure overall water splitting efficiently. Interestingly, at -8% compressive strain, model-I secures type-III band alignment, which is very advantageous for field-effect transistors. In the visible and ultraviolet zones of the radiating spectrum, the proposed vdWHs significantly improved the absorption spectra, and the biaxial strain also has a considerable impact on optical absorption. The investigated vdWHs have high Seebeck coefficients and substantial electrical conductivities, which contribute to high power factor values, particularly at 700 K. The outcomes specify that our designed Ars/SGaInS vdWHs have a multifunctional character that can perform a better role in optoelectronics, photovoltaics, photocatalysis, tunneling field effect transistors, and thermoelectric devices.

Two-dimensional van der Waals heterostructures (vdWHs) with band alignment transformation in multi-functional devices.

Two-dimensional van der Waals heterostructures (vdWHs) with tunable band alignment have the potential to be benignant in the development of minimal multi-functional and controllable electronics, but they have received little attention thus far. It is crucial to characterize and control the band alignment in semiconducting vdWHs, which determines the electronic and optoelectronic properties. The future success of optoelectronic devices will require improved electronic property control techniques, such as using an external electric field or strain engineering, to change the electronic structures directly. Herein, we review heterostructures fabricated as transition metal dichalcogenides (TMDCs) as one of their constituent monolayers with other notable 2D materials that can transfer from type-II to type-III (type-III > type-II) band alignment when a biaxial strain or electric field is applied.

First principles study of optoelectronic and photocatalytic performance of novel transition metal dipnictide XP2 (X = Ti, Zr, Hf) monolayers.

Low cost and highly efficient two dimensional materials as photocatalysts are gaining much attention to utilize solar energy for water splitting and produce hydrogen fuel as an alternative to deal with the energy crisis and reduce environmental hazards. First principles calculations are performed to investigate the electronic, optical and photocatalytic properties of novel two dimensional transition metal dipnictide XP2 (X = Ti, Zr, Hf) monolayers. The studied single layer XP2 is found to be dynamically and thermally stable. TiP2, ZrP2 and HfP2 systems exhibit semiconducting nature with moderate indirect band gap values of 1.72 eV, 1.43 eV and 2.02 eV, respectively. The solar light absorption is found to be in energy range of 1.65-3.3 eV. All three XP2 systems (at pH = 7) and the HfP2 monolayer (at pH = 0) that straddle the redox potentials, are promising candidates for the water splitting reaction. These findings enrich the two dimensional family and provide a platform to design novel devices for emerging optoelectronic and photovoltaic applications.

Theoretical perspective on the electronic structure and optoelectronic properties of type-II SiC/CrS2van der Waals heterostructure with high carrier mobilities.

Two-dimensional heterostructures formed by stacking layered materials play a significant role in condensed matter physics and materials science due to their potential applications in high-efficiency nanoelectronic and optoelectronic devices. In this paper, the structural, electronic, and optical properties of SiC/CrS2van der Waals heterostructure (vdWHs) have been investigated by means of density functional theory calculations. It is confirmed that the SiC/CrS2vdWHs is energetically and thermodynamically stable indicating its great promise for experimental realization. We find that the SiC/CrS2vdWHs has a direct-band gap and type-II (staggered) band alignment, which can effectively separate the photo-induced electrons and holes pairs and extend their life time. The carrier mobilities of electrons and holes along the armchair and zigzag directions are as high as 6.621 × 103and 6.182 × 104 cm2 V-1 s-1, respectively. Besides, the charge difference and potential drop across the interface can induce a large built-in electric field across the heterojunction, which will further hinder the electron and hole recombination. The SiC/CrS2vdWHs has enhanced optical absorption capability compared to individual monolayers. This study demonstrates that the SiC/CrS2vdWHs is a good candidate for application in the nanoelectronic and optoelectronic devices.

Electronic, mechanical, optical and photocatalytic properties of two-dimensional Janus XGaInY (X, Y ;= S, Se and Te) monolayers.

Janus monolayers with breaking out-of-plane structural symmetries and spontaneous electric polarizations offer new possibilities in the field of two-dimensional materials. Due to the depletion of fossil fuels and serious environmental problems, there has been a growing interest in the conversion of water and solar energy into H2 fuels in recent years. In this research, Janus XGaInY (X, Y = S, Se and Te) monolayers are predicted as promising solar-water-splitting photocatalysts. Based on first-principles calculations, the electronic, mechanical, optical and photocatalytic properties of Janus XGaInY (X, Y = S, Se and Te) monolayers are investigated. These Janus monolayers are structurally stable semiconductors with indirect bandgaps, except for SGaInSe, SGaInTe, TeGaInS and SeGaInTe. Their energy bandgaps extend from 0.74 to 2.66 eV at a hybrid density functional level, which is crucial for broadband photoresponses. Moreover, these Janus monolayers not only show strong light absorption coefficients greater than 104 cm-1 in the visible and ultraviolet regions but possess suitable band edge positions for water splitting. Our findings reveal that these Janus monolayers have a potential for application in the fields of optoelectronic and photocatalysis.