InSe/Te van der Waals Heterostructure as a High-Efficiency Solar Cell from Computational Screening

Designing the electronic structures of the van der Waals (vdW) heterostructures to obtain high-efficiency solar cells showed a fascinating prospect. In this work, we screened the potential of vdW heterostructures for solar cell application by combining the group III–VI MXA (M = Al, Ga, In and XA = S, Se, Te) and elementary group VI XB (XB = Se, Te) monolayers based on first-principle calculations. The results highlight that InSe/Te vdW heterostructure presents type-II electronic band structure feature with a band gap of 0.88 eV, where tellurene and InSe monolayer are as absorber and window layer, respectively. Interestingly, tellurene has a 1.14 eV direct band gap to produce the photoexcited electron easily. Furthermore, InSe/Te vdW heterostructure shows remarkably light absorption capacities and distinguished maximum power conversion efficiency (PCE) up to 13.39%. Our present study will inspire researchers to design vdW heterostructures for solar cell application in a purposeful way

Computational mining of the pressure effect on thermodynamic and thermoelectric properties of cubic Ca

Adjusting external pressure has been emerging as one of the most powerful method to unravel the physical and chemical origin of the materials. In this work, we have investigated the pressure effect on thermodynamic and thermoelectric properties of the cubic $Fm\overline 3 m$ phase Ca2Si systematically based on density functional theory within quasi-harmonic approximation and semi-classical Boltzmann transport theory. Our results not only shed light on the origin of the stability of cubic Ca2Si at all the pressures but also provide thermodynamic and thermoelectric maps for cubic Ca2Si under various external pressures. By combining the Seebeck coefficient decreasing and electronic conductivity increasing, the pressure independent power factor of cubic Ca2Si have been highlighted as well. We believe that our findings will facilitate the pressure related applications of Ca2Si in extensive fields

Strain-Enhanced Thermoelectric Performance in GeS2 Monolayer

Strain engineering has attracted extensive attention as a valid method to tune the physical and chemical properties of two-dimensional (2D) materials. Here, based on first-principles calculations and by solving the semi-classical Boltzmann transport equation, we reveal that the tensile strain can efficiently enhance the thermoelectric properties of the GeS2 monolayer. It is highlighted that the GeS2 monolayer has a suitable band gap of 1.50 eV to overcome the bipolar conduction effects in materials and can even maintain high stability under a 6% tensile strain. Interestingly, the band degeneracy in the GeS2 monolayer can be effectually regulated through strain, thus improving the power factor. Moreover, the lattice thermal conductivity can be reduced from 3.89 to 0.48 W/mK at room temperature under 6% strain. More importantly, the optimal ZT value for the GeS2 monolayer under 6% strain can reach 0.74 at room temperature and 0.92 at 700 K, which is twice its strain-free form. Our findings provide an exciting insight into regulating the thermoelectric performance of the GeS2 monolayer by strain engineering

Influence of Al-O and Al-C Clusters on Defects in Graphene Nanosheets Derived from Coal-Tar Pitch via Al₄C₃ Precursor

By treating Al4C3 as the precursor and growth environment, graphene nanosheets (GNs) can efficiently be derived from coal-tar pitch, which has the advantages of simple preparation process, high product quality, green environmental protection, low equipment requirements and low preparation cost. However, the defects in the prepared GNs have not been well understood. In order to optimize the preparation process, based on density functional theory calculations, the influence mechanism of Al-O and Al-C clusters on defects in GNs derived from coal-tar pitch via Al4C3 precursor has been systematically investigated. With minute quantities of oxygen-containing defects, Al-O and Al-C clusters have been realized in the prepared GNs from X-ray photoelectron spectroscopy analysis. Therefore, the influences of Al-O and Al-C clusters on graphene with vacancy defects and oxygen-containing defects are systematically explored from theoretical energy, electron localization function and charge transfer analysis. It is noted that the remaining Al-O and Al-C clusters in GNs are inevitably from the thermodynamics point of view. On the other hand, the existence of defects is beneficial for the further adsorption of Al-O and Al-C clusters in GNs

Efficient Ohmic Contact in Monolayer CrX2N4 (X = C, Si) Based Field‐Effect Transistors

Abstract Developing Ohmic contact systems or achieving low contact resistance is significant for high‐performance semiconductor devices. This work comprehensively investigates the interfacial properties of CrX2N4 (X = C, Si) based field‐effect transistors (FETs) with different metal (Ag, Au, Cu, Ni, Pd, Pt, Ti, and graphene) electrodes by using electronic structure calculations and quantum transport simulations. It is highlighted that the stronger interlayer coupling allows CrC2N4 to form an n‐type Ohmic contact with Ti electrode in the vertical direction. Furthermore, the absence of tunneling barrier at the CrC2N4–Ti interface greatly improves the electron injection efficiency. On the other hand, the studied metals form Schottky contact with CrC2N4 at the lateral interface due to Fermi level pinning (FLP) effects. Surprisingly, the strong FLP effects restrict the Schottky barrier heights of CrSi2N4‐metal contacts to a narrow range. Where Ag, Au, Ni, Pd, Pt, Ti electrodes and Ag, Ti electrodes form ideal ohmic contact with CrSi2N4 in the vertical and lateral directions, respectively, while the other metals form quasi‐ohmic contact. Ti exhibits the highest contact performance as the electrode in both CrC2N4 and CrSi2N4 based FETs. The findings may provide fundamental understanding for designing high‐performance and energy‐efficient FETs based on CrX2N4

Promising M₂CO₂/MoX₂ (M = Hf, Zr; X = S, Se, Te) Heterostructures for Multifunctional Solar Energy Applications

Two-dimensional van der Waals (vdW) heterostructures are potential candidates for clean energy conversion materials to address the global energy crisis and environmental issues. In this work, we have comprehensively studied the geometrical, electronic, and optical properties of M2CO2/MoX2 (M = Hf, Zr; X = S, Se, Te) vdW heterostructures, as well as their applications in the fields of photocatalytic and photovoltaic using density functional theory calculations. The lattice dynamic and thermal stabilities of designed M2CO2/MoX2 heterostructures are confirmed. Interestingly, all the M2CO2/MoX2 heterostructures exhibit intrinsic type-II band structure features, which effectively inhibit the electron-hole pair recombination and enhance the photocatalytic performance. Furthermore, the internal built-in electric field and high anisotropic carrier mobility can separate the photo-generated carriers efficiently. It is noted that M2CO2/MoX2 heterostructures exhibit suitable band gaps in comparison to the M2CO2 and MoX2 monolayers, which enhance the optical-harvesting abilities in the visible and ultraviolet light zones. Zr2CO2/MoSe2 and Hf2CO2/MoSe2 heterostructures possess suitable band edge positions to provide the competent driving force for water splitting as photocatalysts. In addition, Hf2CO2/MoS2 and Zr2CO2/MoS2 heterostructures deliver a power conversion efficiency of 19.75% and 17.13% for solar cell applications, respectively. These results pave the way for exploring efficient MXenes/TMDCs vdW heterostructures as photocatalytic and photovoltaic materials

N6-methyladenosine modification of KLF2 may contribute to endothelial-to-mesenchymal transition in pulmonary hypertension

Abstract Background Pulmonary hypertension (PH) is a progressive disease characterized by pulmonary vascular remodeling. Increasing evidence indicates that endothelial-to-mesenchymal transition (EndMT) in pulmonary artery endothelial cells (PAECs) is a pivotal trigger initiating this remodeling. However, the regulatory mechanisms underlying EndMT in PH are still not fully understood. Methods Cytokine-induced hPAECs were assessed using RNA methylation quantification, qRT-PCR, and western blotting to determine the involvement of N6-methyladenosine (m6A) methylation in EndMT. Lentivirus-mediated silencing, overexpression, tube formation, and wound healing assays were utilized to investigate the function of METTL3 in EndMT. Endothelial-specific gene knockout, hemodynamic measurement, and immunostaining were performed to explore the roles of METTL3 in pulmonary vascular remodeling and PH. RNA-seq, RNA Immunoprecipitation-based qPCR, mRNA stability assay, m6A mutation, and dual-luciferase assays were employed to elucidate the mechanisms of RNA methylation in EndMT. Results The global levels of m6A and METTL3 expression were found to decrease in TNF-α- and TGF-β1-induced EndMT in human PAECs (hPAECs). METTL3 inhibition led to reduced endothelial markers (CD31 and VE-cadherin) and increased mesenchymal markers (SM22 and N-cadherin) as well as EndMT-related transcription factors (Snail, Zeb1, Zeb2, and Slug). The endothelial-specific knockout of Mettl3 promoted EndMT and exacerbated pulmonary vascular remodeling and hypoxia-induced PH (HPH) in mice. Mechanistically, METTL3-mediated m6A modification of kruppel-like factor 2 (KLF2) plays a crucial role in the EndMT process. KLF2 overexpression increased CD31 and VE-cadherin levels while decreasing SM22, N-cadherin, and EndMT-related transcription factors, thereby mitigating EndMT in PH. Mutations in the m6A site of KLF2 mRNA compromise KLF2 expression, subsequently diminishing its protective effect against EndMT. Furthermore, KLF2 modulates SM22 expression through direct binding to its promoter. Conclusions Our findings unveil a novel METTL3/KLF2 pathway critical for protecting hPAECs against EndMT, highlighting a promising avenue for therapeutic investigation in PH