Finding a more flexible mechanical sensor: Piezoelectric materials allow conversion between electricity and mechanical stresses. The most efficient piezoelectric materials are ceramics such as BaTiO ₃ or PbZrO ₃ , which are also extremely stiff. You et al. identified an organic perovskite structured piezoelectric material that is far more pliable yet has a piezoelectric response similar to that of traditional ceramics. This material may be a better option to use as a mechanical sensor for flexible devices, soft robotics, biomedical devices, and other micromechanical applications that benefit from a less stiff piezoelectric material. Science , this issue p. 306

Inspired by natural photosynthesis, direct Z-scheme heterostructures are considered as promising photocatalysts for solar-driven water splitting and attract ever-growing interest. Herein, based on density functional theory and nonadiabatic molecular dynamics calculations, we predict a Janus MoSSe/WSeTe heterostructure as a potential direct Z-scheme photocatalyst for hydrogen evolution. Our calculations show that photogenerated carriers can transfer at the interface via a traditional type II path or Z-scheme path depending on stacking configurations. Surprisingly, introducing surface chalcogen vacancies can not only effectively switch the charge transfer path from type II to Z-scheme, but also increase the time difference between electron (hole) transfer and interlayer carrier recombination with a time scale of 25 ps (37.4 ps), one order of magnitude longer than that of 2595 fs (1531 fs) in intrinsic Z-scheme. This is ascribed to the introduced defect trap states strongly modulating the competition between charge separation and interlayer e–h recombination. These properties make MoSSe/WSeTe heterostructures a compelling direct Z-scheme candidate for photocatalytic hydrogen evolution.

The optical absorption spectra of hexagonal arsenene (β-As) and antimonene (β-Sb).