Accelerating the exploration of material space for hydride double perovskite superconductors under ambient pressure through machine learning.

In the field of hydride superconductors, a great challenge is to achieve superconducting states under ambient pressure conditions rather than the extreme high-pressure environments that have been required in experiments. Achieving this goal is crucial for advancing the practical applications of high-temperature superconducting materials. We discover a family of compounds (hydride double perovskite superconductors with space group Fm3̄m and chemical formula A2MM'H6) to achieves this goal.

Stability and superconductivity of hexagonal prism-structured polyhydrides XMgH (X = Li, Na, K, Rb, Cs) under moderate pressure.

The ultra-high pressure required to maintain hydride superconductors currently limits their further development and practical application, making it urgent to explore stable high-temperature hydride superconductors that can operate at moderate pressures. Here, we conducted an extensive search for various structures with the chemical formula XMgH (X = Li, Na, K, Rb, Cs) and ultimately identified a hexagonal prism hydrogen structure belonging to the space group 2/. Then, we investigated the stability and superconductivity of these structures.

A Cluster-Based Deep Learning Model Perceiving Series Correlation for Accurate Prediction of Phonon Spectrum.

The spectral properties are the most prevalent continuous representation for characterizing transport phenomena and excitation responses, yet their accurate predictions remain a challenge due to the inability to perceive series correlations by existing machine learning (ML) models. Herein, a ML model named cluster-based series graph networks (CSGN) is developed based on the dynamical theory of crystal lattices to predict phonon density of states (PDOS) spectrum for crystal materials. The multiple atomic cluster representation is constructed to capture the diverse vibration modes, while the mixture Gaussian process and dynamic time warping mechanism are compiled to project from clusters to PDOS spectrum.

Rational control of the typical surface defects of hybrid perovskite using tetrahexylammonium iodide.

There are numerous defects existing on the surface and grain boundary of perovskite, which adversely affect the performance and stability of perovskite solar cell devices. Systematic first-principles calculations show that the I vacancy (V), Pb vacancy (V), Pb-I antisite (Pb), and I-Pb antisite (I) defects can significantly affect the electronic properties of the surface of formamidinium lead triiodide (FAPbI); in particular the V, Pb and I surface defects can introduce defect energy levels in the band gap. Tetrahexylammonium iodide (THAI) that is strongly adsorbed on the (1 0 0) surface of FAPbI by forming Pb-I coordination bonds and I⋯H hydrogen bonds could eliminate or reduce the defect states near the band edge or in the band gap by transferring electrons between THAI and the surface of FAPbI.

Superconductivity determined by the S-H framework in CH4-inserted S-H framework hydrides under high pressures.

Recently, a debate is raising the concern of possible carbonaceous sulfur hydrides with room-temperature superconductivity around 270 GPa. In order to systematically investigate the structural information and relevant natures of C-S-H superconductors, we performed an extremely extensive structure search and first-principles calculations under high pressures. As a result, the metastable stoichiometries of CSH7, C2SH14, CS2H10, and CS2H11 were unveiled under high pressure, which can be viewed as CH4 units inserted into the S-H framework.

Surface-Stabilized CsPbI Nanocrystals with Tailored Organic Polymer Ligand Binding.

Perovskite nanocrystals (NCs) exhibit attractive photophysical properties by combining the excellent optoelectronic properties of bulk perovskites with the strong quantum confinement effect at the nanoscale. However, CsPbI NCs easily transform into a non-perovskite phase because of the ionic lattice and dynamic ligand binding. Herein, stable black-phase CsPbI NCs capped with a new organic ligand, HO-PS-N (HOPS), which consists of a polystyrene segment with hydroxyl and azide end groups, are reported.

Optoelectronic simulation of a four-terminal all-inorganic CsPbI/CZTSSe tandem solar cell with high power conversion efficiency.

Tandem solar cells based on perovskites have been gaining ever-increasing attention for applications in photovoltaics. Here, we stack the wide-bandgap CsPbI top subcell with the low-bandgap Kesterite CuZnSnSSe (CZTSSe) bottom subcell mechanically to form a four-terminal tandem solar cell. The thickness of the CsPbI and CZTSSe layers, as well as the thickness of ZnO/ZnS and Spiro-OMeTAD layers are optimized to achieve significantly improved absorption, thereby reducing reflection loss and parasitic absorption.