Strain-stabilized perovskites: The perovskite materials used for solar cells and light-emitting diodes (which are black in color) are generally less stable at room temperature than the electronically inactive nonperovskite phases (which are yellow in color). Steele et al. show that for CsPbI ₃ , strain induced in a thin film after annealing the material to 330°C and then rapidly cooling it to room temperature kinetically trapped the black phase. Grazing-incidence wide-angle x-ray scattering revealed the crystal distortions and texture formation created by interfacial strain. Science , this issue p. 679

The black perovskite phase of CsPbI₃ is promising for optoelectronic applications; however, it is unstable under ambient conditions, transforming within minutes into an optically inactive yellow phase, a fact that has so far prevented its widespread adoption. Here we use coarse photolithography to embed a PbI₂-based interfacial microstructure into otherwise-unstable CsPbI₃ perovskite thin films and devices. Films fitted with a tessellating microgrid are rendered resistant to moisture-triggered decay and exhibit enhanced long-term stability of the black phase (beyond 2.5 years in a dry environment), due to increasing the phase transition energy barrier and limiting the spread of potential yellow phase formation to structurally isolated domains of the grid. This stabilizing effect is readily achieved at the device level, where unencapsulated CsPbI₃ perovskite photodetectors display ambient-stable operation. These findings provide insights into the nature of phase destabilization in emerging CsPbI₃ perovskite devices and demonstrate an effective stabilization procedure which is entirely orthogonal to existing approaches.

Radiation detection, converting high-energy (keV) photons to lower energy (1.7–3 eV) photons, is of great importance in various fields, including medical diagnostics, quality inspection, and security checking. High-resolution scintillation imaging based on lead halide perovskite nanocrystals is very promising for these applications owing to their high absorption cross-section for x-rays, fast decay time, room temperature fabrication, tunable bandgap, low trap density, and near-unity photoluminescence quantum yield. Although considerable achievements have been made, challenges remain for future industrialization. Herein, the progress of scintillators based on lead halide perovskite nanocrystals is reviewed, including their working mechanisms, key parameters, and the relationship between growth conditions and performance. An overview of the current state in this promising research area toward high-performance x-ray scintillators is provided, along with a look at some of the challenges and opportunities that lie ahead.

Direct conversion X-ray detectors based on metal halide perovskites (MHPs), notably CsPbBr ₃ , promise high performance but suffer from detrimental dark currents and ion migration.

An interfacial electric field strategy effectively enhances the performance of perovskite X-ray detectors.