Researchers from Japan's Tokyo Institute of Technology, University of Oxford in the UK and Colorado State University in the U.S have shown that α-FAPbI₃, a promising solar cell material with a cubic perovskite structure that is metastable at room temperature, can be stabilized by introducing a pseudo-halide ion like thiocyanate (SCN^–) into its structure. The recent findings provide new insights into the stabilization of the α-phase via grain boundary and pseudo-halide engineering.

A material with good photophysical properties that has recently gained momentum is α-formamidinium lead iodide or α-FAPbI₃ (where FA⁺ = CH(NH₂)₂⁺), a crystalline solid with a cubic perovskite structure. Solar cells made of α-FAPbI₃ exhibit a remarkable 25.8% conversion efficiency and an energy gap of 1.48 eV. Unfortunately, α-FAPbI₃ is metastable at room temperature and undergoes a phase transition to δ-FAPbI₃ when triggered by water or light. The energy gap of δ-FAPbI₃ is much larger than the ideal value for solar cell applications, making the preservation of the α-phase crucial for practical purposes. To overcome this problem, the team of researchers, led by Associate Professor Takafumi Yamamoto from Tokyo Institute of Technology (Tokyo Tech), has recently presented a new strategy for stabilizing α-FAPbI₃.

Researchers from The University of Texas at Austin, University of Pennsylvania and Massachusetts Institute of Technology (MIT) have addressed the question of how lattice dynamics in layered hybrid perovskites are affected by the dimensional engineering of the inorganic frameworks and their interaction with the molecular moieties. 

The team tackled this question by using a combination of spontaneous Raman scattering, terahertz spectroscopy, and molecular dynamics simulations. This approach reveals the structural dynamics in and out of equilibrium and provides unexpected observables that differentiate single- and double-layered perovskites.

Researchers from Duke University and North Carolina State University have reported glass formation for low-melting-temperature 1-MeHa₂PbI₄ (1-MeHa = 1-methyl-hexylammonium) using ultrafast calorimetry, thereby extending the range of metal halide perovskite (MHP) glass formation across a broader range of organic (fused ring to branched aliphatic) and halide (bromide to iodide) compositions. 

A few years ago, Akash Singh and collaborators at Duke University set out to explore the realm of glassy perovskites, a departure from the traditionally studied crystalline perovskites. Since then, this topic sparked interest, resulting in the establishment of a novel research domain centered around glass-forming hybrid perovskite semiconductors with reversible switching. This recent discovery of glass formation in MHPs opens new opportunities associated with reversible glass-crystalline switching, with each state offering distinct optoelectronic properties. However, the previously reported [S-(−)-1-(1-naphthyl)ethylammonium]₂PbBr₄ perovskite is a strong glass former with sluggish glass-crystal transformation time scales, pointing to a need for glassy MHPs with a broader range of compositions and crystallization kinetics.   

Researchers from Texas A&M University, Northwestern University, University of South Florida and University of Illinois Urbana-Champaign have studied the fatigue behavior of 2D hybrid organic-inorganic perovskites (HOIPs) in practical applications.

The application of repeated or fluctuating stresses below the material's strength, known as fatigue loading, often leads to failure in 2D hybrid materials. However, the fatigue properties of HOIP materials have remained elusive despite their widespread use in various applications. The research group demonstrated how fatigue loading conditions, wearing different components, would affect the lifetime and failure behavior of the materials. Their results provide insights into designing and engineering 2D HOIPs and other hybrid organic-inorganic materials for long-term mechanical durability.

Researchers from North Carolina State University, National Synchrotron Light Source II at Brookhaven National Laboratory and Rey Juan Carlos University have created a novel materials acceleration platform (MAP), essentially a robot capable of conducting experiments more efficiently and sustainably to develop a range of new semiconductor materials with desirable attributes. The researchers have demonstrated that the new technology, called RoboMapper, can rapidly identify new perovskite materials with favorable properties and improved potential for creating stable and efficient solar cells.

“RoboMapper allows us to conduct materials testing more quickly, while also reducing both cost and energy overhead – making the entire process more sustainable,” says Aram Amassian, corresponding author of a paper on the work and a professor of materials science and engineering at North Carolina State University.

Researchers at MIT have prepared large CsPbBr₃ nanocrystals and observed direct evidence of interference between indistinguishable single photons sequentially emitted from a single nanocrystal. 

While the work is currently a fundamental discovery of these materials' capabilities, it might ultimately pave the way to new optically based quantum computers, as well as possible quantum teleportation devices for communication, the researchers say. 

Researchers at Florida State University, the FAMU-FSU College of Engineering, the University of Colorado Boulder and Argonne National Laboratory have studied the effects of two stressors, heat and light, on the triplet generation process at the perovskite/rubrene interface. Following exposure to both stressors, local discrepancies across the upconversion device were discovered. This work emphasizes the challenges and continued potential for the integration of perovskite-sensitized upconversion (UC) into commercial photovoltaic devices. 

The first region showed changes to the morphology, and no detectable upconverted emission was observed. Through the combination of optical microscopy and spectroscopy, crystallization of the organic semiconductor layer, degradation of dibenzotetraphenylperiflanthene, and concurrent degradation of the perovskite sensitizer were found. These effects culminate in a reduction in both triplet generation and triplet–triplet annihilation. In the second region, no changes to the morphology were present and visible UC emission was observed following exposure to both stressors. To probe the triplet sensitization process at elevated temperatures, transient absorption spectroscopy was performed. The presence of the excited spin-triplet state of rubrene at 60 °C highlighted successful triplet generation even at elevated temperatures. 

Researchers from the Chinese Academy of Sciences (CAS) have used graphdiyne oxide (GDYO), fluorinated GDYO (FGDYO) and nitrogen-doped GDYO (NGDYO) to improve the SnO₂ electron transport layer (ETL) in perovskite solar cells and revealed the relevant mechanism using synchrotron radiation technology. 

The team tracked the growth process of SnO₂, PbI₂ and perovskite using in situ XRD and the chemical bonds on the interface between ETL and the active layer using in situ XAFS. They found that the stronger interaction between the doped SnO₂ and PbI₂ inhibited PbI₂ crystallization in perovskite layers and gave more opportunity for the PbI₂ precursor to form perovskite, thus making perovskite crystallize better.

Researchers from Ames National Laboratory worked with scientists at the Swiss Federal Institute of Technology in Zürich (ETH Zurich) to understand how to assemble perovskites (that are shaped as nanocubes) with other sphere-shaped nanocrystals. 

The scientists used the Expanse supercomputer at the San Diego Supercomputer Center (SDSC) at UC San Diego to identity the general rules that enable the assembly of nanocubes like perovskites with spherical nanoparticles. Ultimately, they conducted a study to assist with the design of future nanoparticle-based materials. Their recent paper provides details on both their results and problems when pairing the perovskites with spherical nanocrystals.

An international team of scientists from Fritz Haber Institute of the Max Planck Society, École Polytechnique in Paris, Columbia University in New York, and the Free University in Berlin have demonstrated laser-driven control of fundamental motions of the lead halide perovskite (LHP) atomic lattice.

Sketch of the experimental pump-probe configuration. Image from Science Advances

By applying a sudden electric field spike faster than a trillionth of a second (picosecond) in the form of a single light cycle of far-infrared Terahertz radiation, the team unveiled the ultrafast lattice response, which might contribute to a dynamic protection mechanism for electric charges. This precise control over the atomic twist motions could allow to create novel non-equilibrium material properties, potentially providing hints for designing the solar cell material of the future.