We explored the possibility of enhancing interfacial conductivity and spatial charge confinement of LaAlO3/SrTiO3 (LAO/STO) heterostructure (HS) via strain engineering using first-principles electronic structure calculations. We found that applying a tensile strain on the STO substrate along the ab-plane can significantly enhance the interfacial conductivity, magnetic moments, and the spatial charge confinement of the HS system. In contrast, a compressive strain can dilute the interfacial charge carrier density, make the mobile charges transfer to deep STO substrate, and weaken the spatial charge confinement along the c-axis. Hence, we propose that applying a tensile strain can be an effective way to enhance the interfacial conductivity and magnetism of STO-based HS systems.

The two-dimensional electron gas (2DEG) formed at the interface between two insulating oxides such as LaAlO3 and SrTiO3 (STO) is of fundamental and practical interest because of its novel interfacial conductivity and its promising applications in next-generation nanoelectronic devices. Here we show that a group of combinatorial descriptors that characterize the polar character, lattice mismatch, band gap, and the band alignment between the perovskite-oxide-based band insulators and the STO substrate, can be introduced to realize a high-throughput (HT) design of SrTiO3-based 2DEG systems from perovskite oxide quantum database. Equipped with these combinatorial descriptors, we have carried out a HT screening of all the polar perovskite compounds, uncovering 42 compounds of potential interests. Of these, Al-, Ga-, Sc-, and Ta-based compounds can form a 2DEG with STO, while In-based compounds exhibit a strain-induced strong polarization when deposited on STO substrate. In particular, the Ta-based compounds can form 2DEG with potentially high electron mobility at (TaO2)+/(SrO)0 interface. Our approach, by defining materials descriptors solely based on the bulk materials properties, and by relying on the perovskite-oriented quantum materials repository, opens new avenues for the discovery of perovskite-oxide-based functional interface materials in a HT fashion.

Organic–inorganic hybrid perovskites with a prototype formula MAPbI3 (MA = CH3NH3) have shown great promise in next-generation solar cells, yet a full understanding of their high power conversion efficiency relative to their inorganic counterparts has not been achieved. One of the most plausible arguments for their high efficiency is the ability of organic cations to form ferroelectric (FE) domains. By using first-principles calculations to examine the rotational behavior of MA cations in MAPbI3, here we show a relationship between the lattice structures and the FE dipole ordering of MA cations. It is found that the MA cations could form a spontaneous FE dipole ordering in tetragonal MAPbI3 at room temperature. The tendency of the FE formation is strongly related to the ratio of lattice parameters of MAPbI3. On the basis of the developed structure–ferroelectric-property relationship, we propose that a biaxial or uniaxial compressive strain and an anion doping with small halogen ions can further enhance the FE dipole ordering. These findings are in good agreement with the experimental discoveries that high-performance solar cells always incorporate mixed halide hybrid perovskites involving Br or Cl ions. This work may provide some guidelines for rational designs of highly efficient hybrid perovskite solar cells.

We studied the influence of uniaxial [100] strain (-1% to +1%) on the electron transport properties of a two-dimensional electron gas (2DEG) at the n-type interface of the LaAlO3/SrTiO3(LAO/STO) heterostructure (HS)-based slab system from the perspective of polarization effects via first-principles density functional theory calculations. We first analyzed the unstrained system, and found that the induced polarization toward the vacuum in the LAO film leads to a small charge carrier density on the order of 10(13) cm(-2) (less than the theoretical value of 3.3 × 10(14) cm(-2) from the superlattice-model-based polar catastrophe mechanism), which is in excellent agreement with the experimental values of oxygen-annealed LAO/STO HS samples. Upon applying [100] tensile strain on the STO substrate, we found a significant reduction of the induced polarization in the LAO film. This reduction weakens the driving force against charge transfer from LAO to STO, causing an increase in the interfacial charge carrier density. The uniaxial strain also leads to a decrease of the effective mass of interfacial mobile electrons, resulting in a higher electron mobility. These findings suggest that applying uniaxial [100] tensile strain on the STO substrate can significantly enhance the interfacial conductivity of the LAO/STO HS system, which gives a comprehensive explanation for experimental observations. In contrast, compressively strained LAO/STO systems show stronger LAO film polarization than the unstrained system, which reduces the interfacial charge carrier density and increases the electron effective mass, thus suppressing the interfacial conductivity.