Organic materials that exhibit thermally activated delayed fluorescence (TADF) are an attractive class of functional materials that have witnessed a booming development in recent years. Since Adachi et al. reported high-performance TADF-OLED devices in 2012, there have been many reports regarding the design and synthesis of new TADF luminogens, which have various molecular structures and are used for different applications. In this review, we summarize and discuss the latest progress concerning this rapidly developing research field, in which the majority of the reported TADF systems are discussed, along with their derived structure–property relationships, TADF mechanisms and applications. We hope that such a review provides a clear outlook of these novel functional materials for a broad range of scientists within different disciplinary areas and attracts more researchers to devote themselves to this interesting research field.

Recent advances in organic thermally activated delayed fluorescence materials.

Halide perovskites have recently emerged as promising materials for low-cost, high-efficiency solar cells. The efficiency of perovskite-based solar cells has increased rapidly, from 3.8% in 2009 to 19.3% in 2014, by using the all-solid-state thin-film architecture and engineering cell structures with mixed-halide perovskites. The emergence of perovskite solar cells revolutionized the field not only because of their rapidly increased efficiency, but also flexibility in material growth and architecture. The superior performance of the perovskite solar cells suggested that perovskite materials possess intrinsically unique properties. In this review, we summarize recent theoretical investigations into the structural, electrical, and optical properties of halide perovskite materials in relation to their applications in solar cells. We also discuss some current challenges of using perovskites in solar cells, along with possible theoretical solutions.

Halide perovskite materials for solar cells: a theoretical review

Boron, a nearest-neighbor of carbon, is possibly the second element that can possess free-standing flat monolayer structures, evidenced by recent successful synthesis of single-walled and multiwalled boron nanotubes (MWBNTs). From an extensive structural search using the first-principles particle-swarm optimization (PSO) global algorithm, two boron monolayers (α1- and β1-sheet) are predicted to be the most stable α- and β-types of boron sheets, respectively. Both boron sheets possess greater cohesive energies than the state-of-the-art two-dimensional boron structures (by more than 60 meV/atom based on density functional theory calculation using PBE0 hybrid functional), that is, the α-sheet previously predicted by Tang and Ismail-Beigi and the g1/8- and g2/15-sheets (both belonging to the β-type) recently reported by Yakobson and co-workers. Moreover, the PBE0 calculation predicts that the α-sheet is a semiconductor, while the α1-, β1-, g1/8-, and g2/15-sheets are all metals. When two α1 monolayers are sta...

Two-Dimensional Boron Monolayer Sheets

We report experimental results that show a large and symmetric population of D and L crystals moving
into complete chiral purity, with one of the enantiomers completely disappearing. The results indicate (i) a
new symmetry breaking process incompatible with the hypothesis of an initial single chiral phase or
‘‘mother crystal,’’ (ii) that total symmetry breaking and complete chiral purity can be achieved from a
system that initially includes both enantiomers, and (iii) that this is achieved through a nonlinear
autocatalytic-recycling process.

Chiral Symmetry Breaking during Crystallization: Complete Chiral Purity induced by Nonlinear Autocatalysis and Recycling

When two single Rydberg atoms—those with electrons in highly excited states—interact, one can be used to control the quantum state of the other. Two independent experiments demonstrate such ‘Rydberg blockade’, an effect that might make long-range quantum gates between neutral atoms possible.

Collective excitation of two individual atoms in the Rydberg blockade regime

The triangular boron lattice has too many electrons, and the hexagonal lattice has too few. But a hybrid of the two is just right.

https://physicstoday.scitation.org/doi/pdf/10.1063/1.2812113

New sheet structures may be the basis for boron nanotubes

First-principles calculations provide insight into one of the newest and most promising classes of materials for photovoltaic devices.

https://physicstoday.scitation.org/doi/pdf/10.1063/PT.3.2368

Unusual defect physics underlies perovskite solar cells’ exceptional performance

Whether long-range magnetic order could survive in the 2D limit was an open and fundamental question. The answer is that it can, but it has some surprises in store.

Ferromagnetism found in two-dimensional materials

At just the right locations in parameter space, resonant frequencies are ultrasensitive to tiny changes in conditions.

https://physicstoday.scitation.org/doi/pdf/10.1063/PT.3.3717

Exceptional points make for exceptional sensors

Detecting the tiny magnetic field from a few thousand atomic nuclei is a first step toward imaging molecular structures directly. Detecting the tiny magnetic field from a few thousand atomic nuclei is a first step toward imaging molecular structures directly.

Johanna L. Miller

Papers

New sheet structures may be the basis for boron nanotubes

Unusual defect physics underlies perovskite solar cells’ exceptional performance

Ferromagnetism found in two-dimensional materials

Exceptional points make for exceptional sensors

Nanoscale nuclear magnetic resonance