One‑Step Gas-Solid‑Phase Diffusion‑Induced Elemental Reaction for Bandgap‑Tunable Cu_(a)Agm_(1)Bim_(2)I_(n)/CuI Thin Film Solar Cells

Lead-free inorganic copper-silver-bismuth-halide materials have attracted more and more attention due to their environmental friendliness,high element abundance,and low cost.Here,we developed a strategy of one-step gas-solid-phase diffusioninduced reaction to fabricate a series of bandgap-tunable Cu_(a)Agm_(1)Bim_(2)I_(n)/CuI bilayer films due to the atomic diffusion effect for the first time.By designing and regulating the sputtered Cu/Ag/Bi metal film thickness,the bandgap of Cu_(a)Agm_(1)Bim_(2)I_(n)/CuI could be reduced from 2.06 to 1.78 eV.Solar cells with the structure of FTO/TiO_(2)/Cu_(a)Agm_(1)Bim_(2)I_(n)/CuI/carbon were constructed,yielding a champion power conversion efficiency of 2.76%,which is the highest reported for this class of materials owing to the bandgap reduction and the peculiar bilayer structure.The current work provides a practical path for developing the next generation of efficient,stable,and environmentally friendly photovoltaic materials.

Engineering of electronic and optical properties of ZnO thin films via Cu doping

ZnO thin films doped with different Cu concentrations are fabricated by reactive magnetron sputtering technique. XRD analysis indicates that the crystal quality of the ZnO：Cu film can be enhanced by a moderate level of Cu-doping in the sputtering process. The results of XPS spectra of zinc, oxygen, and copper elements show that Cu-doping has an evident and complicated effect on the chemical state of oxygen, but little effect on those of zinc and copper. Interestingly, further investigation of the optical properties of ZnO：Cu samples shows that the transmittance spectra exhibit both red shift and blue shift with the increase of Cu doping, in contrast to the simple monotonic behavior of the Burstein–Moss effect. Analysis reveals that this is due to the competition between oxygen vacancies and intrinsic and surface states of oxygen in the sample. Our result may suggest an effective way of tuning the bandgap of ZnO samples.

Geometrically induced π-band splitting in graphene superlattices

According to band folding analyses, the graphene superlattices can be differed by whether the Dirac points are folded to Γ point or not. In previous studies, the inversion symmetry preserved defects open bandgap in the former superlattices while they cannot in the latter ones. In this paper, by using density functional theory with generalized gradient approximation, we have carefully studied the electronic properties of the latter graphene superlattices, in which the defects would induce π-band splitting to get the π_a1–π_a2 and π_z1–π_z2 band sets. Based on our detailed studies, such splitting could be attributed to the geometrically induced bond-symmetry breaking. In addition, these band sets could be shifted toward each other by the methodology of strain engineering. A bandgap would be opened once the band sets start to overlap. Then,its gap width could be continuously enlarged by enhancing strain until reaching the maximum value determined by the defect density. These studies contribute to the bandstructure engineering of graphene-based nanomaterials, which would be interesting to call for further investigations on both theory and experiment.

Advances in two-dimensional molybdenum ditelluride(MoTe2):A comprehensive review of properties,preparation methods,and applications

In the past decade,molybdenum ditelluride(MoTe2)has received significant attention from the scientific community due to its structural features and unique properties originate from them.In the current review,the properties,various preparation approaches,and versatile applications of MoTe2 are presented.The review provides a brief update on the state of our fundamental understanding of MoTe2 material and also discusses the issues that need to be resolved.To introduce MoTe2,we briefly summarize its structural,optoelectronic,magnetic,and mechanical properties in the beginning.Then,different preparation meth-ods of MoTe2,such as exfoliation,laser treatment,deposition,hydrothermal,microwave,and molecular beam epitaxy,are included.The excellent electri-cal conductivity,strong optical activity,tunable bandgap,high sensitivity,and impressive stability make it an ideal contender for different applications,includ-ing energy storage,catalysis,sensors,solar cells,photodetectors,and transistors.The performance of MoTe2 in these applications is systematically introduced along with mechanistic insights.At the end of the article,the challenges and possible future directions are highlighted to further modify MoTe2 material for the numerous functionalities.Therefore,the availability of different phases and layer structures implies a potential for MoTe2 to lead an era of two-dimensional materials that began from the exfoliation of graphene.

Unlocking the Potential of Halide Perovskites Through Doping

Halide perovskites have become a hot topic in materials research due to their potential applications in a variety of fields,from optoelectronic and thermoelectric devices to solar cells.Doping of halide perovskites can be achieved by introducing different types of dopants,such as metal cations,anions,and organic molecules,leading to increased stability and improved optoelectronic properties.Moreover,doping can introduce new functionalities,such as increased spin lifetime and thermal stability.These features make doped halide perovskites a highly promising candidate for optoelectronic applications.In this mini-review,we highlight the latest advances in ion-doped halide perovskites and their immense potential for various applications.