Searching for novel, high-performance, two-dimensional photovoltaic (2DPV) materials is an important pursuit for solar cell applications. In this work, an efficient method based on the machine learning algorithm combined with high-throughput screening is developed. Twenty-six 2DPV candidates are successfully ruled out from 187093 experimentally identified inorganic crystal structures, whose conversion efficiencies are predicted by density functional theory calculations. Our results indicate that Sb2Se2Te, Sb2Te3, and Bi2Se3 exhibit conversion efficiencies that are much higher than those of others, which make them promising 2DPV candidates for further applications. The superior photovoltaic performance is then analyzed, and the hidden structure-related relationships with photovoltaic properties are established, thus providing important information for the further examination of 2DPV materials. Given the rapid development of the database of materials, this approach not only provides an efficient way of searching for novel 2DPV materials but also can be applied to exploration of a broad range of functional materials.

As conventional Si-based devices approach their scaling limit, it is of great significance to find new materials for future electronic logic devices. The emerging two-dimensional (2D) materials with atomic thickness have attracted intense interests for their exotic properties. However, the presence of the Schottky barrier limits their applications, which is difficult to control over due to the Fermi level pinning effect. Therefore, searching for low resistance metal contact to 2D semiconductors becomes one of the most important topics. Here, we report that Ohmic contact can be realized in a monolayer InSe–Cu system. Based on the density functional theory combined with the nonequilibrium Green’s functions, the geometry, overlapping states, tunneling barrier, Schottky barrier, and band alignment at the interface of group-IB (Cu, Ag, and Au) with InSe monolayer are discussed in details. Our results reveal that Cu, the most common electrode used in the industry, shows great potential to form favorable contact with single layer InSe due to the strong interaction and high orbital overlapping. The calculated drain-source current versus bias voltage (I  −  V) curve exhibits linear behavior, indicating good Ohmic contact between the Cu electrodes and InSe channel. Our work may pave the way for design of next-generation ultrathin and flexible devices.

In the presence of a non-local potential arising from electron-electron interaction, the conventional definition of current density J(c) = (e/2m)([(p-eA)ψ](*)ψ-ψ(*)[(p-eA)ψ]) cannot satisfy the condition of current conservation, i.e., [Formula: see text] in the steady state. In order to solve this problem, we give a new definition of current density including the contribution due to the non-local potential. We show that the current calculated based on the new definition of current density conserves the current and is the same as that obtained from the Landauer-Büttiker formula. Examples are given to demonstrate our results.

We investigate the thermoelectric transport through carbon chains connected by two Al leads. Using a Landauer-Buttiker-like formula, we calculate the thermopower and thermoconductance of Al-C n-Al from first principles. We find that the charge transfer plays an important role in the thermoelectric transport. Because of the charge transfer, the thermopower changes sign for even-odd number of carbon atoms. The thermopower and electric conductance as a function of the gate voltage also exhibit oscillatory behaviors with a phase difference of /2.

Searching for highly efficient, environmentally friendly, and noble metal free photocatalysts is an important topic in the photocatalytic field. The combination of data-driven high-throughput screening and density functional theory (DFT) might be one of the most effective ways. To this end, we have carried out a systematic search of the Materials Project Database. A high-throughput screening method is employed, and six criteria are selected as the indicators. The screening reduces the list of candidates from 83989 to 22 structures that show promise as photocatalysts. The electronic and optical properties are then determined by DFT calculations. Our results indicate that ZnSe, Ga2Se3, and Na2Zn2O3 show suitable direct band gaps, efficient optical absorption, and appropriate band edge positions, which are suitable for photocatalytic water splitting in the visible light region. We believe that this work not only proposes novel photocatalysts but also provides an efficient way of searching for advanced photocatalysts for water splitting.