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The Lewis acidity of trihaloboranes has now also been observed for tetrahalodiboranes, which bind halides to give hexahalodiborates — a new anion class.

Metal-halide perovskite light-emitting diodes (PeLEDs) have attracted great interest because of their tunable emission wavelength, narrow emission bandwidth and high external quantum efficiency. However, PeLEDs face two critical issues that limit their potential applications: short device lifetime due to ion migration and low brightness due to severe Auger recombination. Here we demonstrate that both issues can be mitigated by in situ solution-grown perovskite single crystals (SCs). By minimizing the trap density using mixed cations and adding excess ammonium halides and polyvidone to the precursor, the external photoluminescence quantum yield (PLQY) of the SCs is enhanced to 28.3%, corresponding to an internal PLQY of 89.4%. Benefitting from the suppressed Auger recombination in SCs, SC-PeLEDs with a thickness of 1.5 µm exhibit a high luminance of 86,000 cd m−2 and a peak external quantum efficiency of 11.2%. Thanks to suppressed ion migration, the extrapolated T50 lifetime for SC-PeLEDs reaches a value of 12,500 h at an initial luminance of 100 cd m−2. Our results show that SC growth represents a viable route to increase the lifetime of PeLEDs for practical applications.Single-crystal perovskite LEDs exhibit reduced ion migration and Auger recombination and increased device lifetime. Perovskite single-crystals-based LEDs exhibit a maximum brightness of 86,000 cd m−2, a peak EQE of 11.2% and T50 lifetime of 12,500 h at an initial luminance of 100 cd m−2.

Wide–band gap metal halide perovskites are promising semiconductors to pair with silicon in tandem solar cells to pursue the goal of achieving power conversion efficiency (PCE) greater than 30% at low cost. However, wide–band gap perovskite solar cells have been fundamentally limited by photoinduced phase segregation and low open-circuit voltage. We report efficient 1.67–electron volt wide–band gap perovskite top cells using triple-halide alloys (chlorine, bromine, iodine) to tailor the band gap and stabilize the semiconductor under illumination. We show a factor of 2 increase in photocarrier lifetime and charge-carrier mobility that resulted from enhancing the solubility of chlorine by replacing some of the iodine with bromine to shrink the lattice parameter. We observed a suppression of light-induced phase segregation in films even at 100-sun illumination intensity and less than 4% degradation in semitransparent top cells after 1000 hours of maximum power point (MPP) operation at 60°C. By integrating these top cells with silicon bottom cells, we achieved a PCE of 27% in two-terminal monolithic tandems with an area of 1 square centimeter.

Achieving both high efficiency and long-term stability is the key to the commercialization of perovskite solar cells (PSCs) 1 , 2 . However, the diversity of perovskite (ABX 3 ) compositions and phases makes it challenging to fabricate high-quality films 3 – 5 . Perovskite formation relies on the reaction between AX and BX 2 , whereas most conventional methods for film-growth regulation are based solely on the interaction with the BX 2 component. Herein, we demonstrate an alternative approach to modulate reaction kinetics by anion–π interaction between AX and hexafluorobenzene (HFB). Notably, these two approaches are independent but work together to establish ‘dual-site regulation’, which achieves a delicate control over the reaction between AX and BX 2 without unwanted intermediates. The resultant formamidinium lead halides (FAPbI 3 ) films exhibit fewer defects, redshifted absorption and high phase purity without detectable nanoscale δ phase. Consequently, we achieved PSCs with power conversion efficiency (PCE) up to 26.07% for a 0.08-cm 2 device (25.8% certified) and 24.63% for a 1-cm 2 device. The device also kept 94% of its initial PCE after maximum power point (MPP) tracking for 1,258 h under full-spectrum AM 1.5 G sunlight at 50 ± 5 °C. This method expands the range of chemical interactions that occur in perovskite precursors by exploring anion–π interactions and highlights the importance of the AX component as a new and effective working site to improved photovoltaic devices with high quality and phase purity. The use of anion–π interactions during perovskite film formation is shown to give better quality perovskite layers with high phase purity, leading to improved photovoltaic devices with high power conversion efficiency.

Dynamically responsive materials, capable of reversible changes in color appearance and/or photoemission upon external stimuli, have attracted substantial attention across various fields. This study presents an effective approach wherein switchable modulation of photochromism and ultralong phosphorescence can be achieved simultaneously in a zero-dimensional organic-inorganic halide hybrid glass doped with 4,4´-bipyridine. The facile fabrication of large-scale glasses is accomplished through a combined grinding-melting-quenching process. The persistent luminescence can be regulated through the photochromic switch induced by photo-generated radicals. Furthermore, the incorporation of the aggregation-induced chirality effect generates intriguing circularly polarized luminescence, with an optical dissymmetry factor ( g lum ) reaching the order of 10 –2 . Exploiting the dynamic ultralong phosphorescence, this work further achieves promising applications, such as three-dimensional optical storage, rewritable photo-patterning, and multi-mode anti-counterfeiting with ease. Therefore, this study introduces a smart hybrid glass platform as a new photo-responsive switchable system, offering versatility for a wide array of photonic applications. Dynamically responsive afterglow materials are typically fabricated as single crystals, polymers or powders. Here, the authors use zero-dimensional metal halides and organic dopants to develop photochromic glasses for diverse optical applications.

A highly efficient magnetic nanocomposite, Pd/MnFe.sub.2O.sub.4 has been prepared by citrate gel auto combustion and deposition precipitation method for reductive Ullmann homocoupling of aryl halides in an aqueous medium. The physical and chemical properties of the synthesized composite were characterized by XRD, TEM, SEM, EDAX, VSM, and BET analysis. The synthesis of symmetrical biaryls has been achieved at admirable reaction conditions with high yield in a short reaction time. The nanocomposite catalyst could be easily separated by magnetic separation and recycled up to six reaction cycles with appreciable yields of desired products. The synthesized nanocomposite was found to be a best alternative catalyst for carbon-carbon bond formation in Ullmann-type homocoupling.

Facile protocol for the synthesis of biaryls from aryl halides in presence of magnesium metal without prior formation of organometallic intermediate has been exploited. Irrespective of aqueous medium, Ti.sub.0.97Pd.sub.0.03O.sub.1.97 catalyst supports C-C bond formation reaction in presence of metals rather than dehalogenation without any additives. Homocoupling of 16 different aryl halides furnished corresponding biphenyls in good yield with better functional group tolerance. The recovery of the catalyst was carried out by employing catalyst coated cordierite monolith up to 7th cycle with high yields. A new approach for the cross-coupling reaction is also attempted.

Atomically defined assemblies of dye molecules (such as H and J aggregates) have been of interest for more than 80 years because of the emergence of collective phenomena in their optical spectra 1 – 3 , their coherent long-range energy transport, their conceptual similarity to natural light-harvesting complexes 4 , 5 , and their potential use as light sources and in photovoltaics. Another way of creating versatile and controlled aggregates that exhibit collective phenomena involves the organization of colloidal semiconductor nanocrystals into long-range-ordered superlattices 6 . Caesium lead halide perovskite nanocrystals 7 – 9 are promising building blocks for such superlattices, owing to the high oscillator strength of bright triplet excitons 10 , slow dephasing (coherence times of up to 80 picoseconds) and minimal inhomogeneous broadening of emission lines 11 , 12 . So far, only single-component superlattices with simple cubic packing have been devised from these nanocrystals 13 . Here we present perovskite-type (ABO 3 ) binary and ternary nanocrystal superlattices, created via the shape-directed co-assembly of steric-stabilized, highly luminescent cubic CsPbBr 3 nanocrystals (which occupy the B and/or O lattice sites), spherical Fe 3 O 4 or NaGdF 4 nanocrystals (A sites) and truncated-cuboid PbS nanocrystals (B sites). These ABO 3 superlattices, as well as the binary NaCl and AlB 2 superlattice structures that we demonstrate, exhibit a high degree of orientational ordering of the CsPbBr 3 nanocubes. They also exhibit superfluorescence—a collective emission that results in a burst of photons with ultrafast radiative decay (22 picoseconds) that could be tailored for use in ultrabright (quantum) light sources. Our work paves the way for further exploration of complex, ordered and functionally useful perovskite mesostructures. Through precise structural engineering, perovskite nanocrystals are co-assembled with other nanocrystal materials to form a range of binary and ternary perovskite-type superlattices that exhibit superfluorescence.

Solution-processed metal-halide perovskites are emerging as one of the most promising materials for displays, lighting and energy generation. Currently, the best-performing perovskite optoelectronic devices are based on lead halides and the lead toxicity severely restricts their practical applications. Moreover, efficient white electroluminescence from broadband-emission metal halides remains a challenge. Here we demonstrate efficient and bright lead-free LEDs based on cesium copper halides enabled by introducing an organic additive (Tween, polyethylene glycol sorbitan monooleate) into the precursor solutions. We find the additive can reduce the trap states, enhancing the photoluminescence quantum efficiency of the metal halide films, and increase the surface potential, facilitating the hole injection and transport in the LEDs. Consequently, we achieve warm-white LEDs reaching an external quantum efficiency of 3.1% and a luminance of 1570 cd m −2 at a low voltage of 5.4 V, showing great promise of lead-free metal halides for solution-processed white LED applications. Designing efficient light-emitting diodes with white-light-emission from broadband-emission metal halides remains a challenge. Here, the authors demonstrate bright and efficient lead-free LEDs based on cesium copper halides enabled by introducing Tween organic additive in the precursor.