Are Shockley-Read-Hall and ABC models valid for lead halide perovskites?

Metal halide perovskites are an important class of emerging semiconductors. Their charge dynamics is poorly understood due to limited knowledge of defect physics and charge recombination mechanisms. Nevertheless, classical ABC and Shockley-Read-Hall (SRH) models are ubiquitously applied to perovskites without considering their validity. Herein, an advanced technique mapping photoluminescence quantum yield (PLQY) as a function of both the excitation pulse energy and repetition frequency is developed and employed to examine the validity of these models. While ABC and SRH fail to explain the charge dynamics in a broad range of conditions, the addition of Auger recombination and trapping to the SRH model enables a quantitative fitting of PLQY maps and low-power PL decay kinetics, and extracting trap concentrations and efficacies. Higher-power PL kinetics requires the inclusion of additional non-linear processes. The PLQY mapping developed herein is suitable for a comprehensive testing of theories and is applicable to any semiconductor.Comment: Supplementary Information available at https://cloudstore.zih.tu-dresden.de/index.php/s/t5gBPJgwZiwfRR

Fluorescent Phase-Pure Zero-Dimensional Perovskite-Related Cs₄PbBr₆ Microdisks: Synthesis and Single-Particle Imaging Study

Quantum-confined perovskites are a new class of promising materials in optoelectronic applications. In this context, a zero-dimensional perovskite-related substance, Cs₄PbBr₆, having high exciton binding energy can be an important candidate, but its photoluminescence (PL) is a topic of recent debate. Herein, we report an ambient condition controlled synthesis of Cs₄PbBr₆ microdisks of different shapes and dimensions which exhibit fairly strong green PL (quantum yield up to 38%, band gap ∼2.43 eV) in the solid state. Using confocal fluorescence microscopy imaging of the single particles, we show that the fluorescence of Cs₄PbBr₆ microdisks is inherent to these particles. Fluorescence intensity and lifetime imaging of the microdisks reveals significant spatial heterogeneity with a bright central area and somewhat dimmer edges. This intensity and lifetime distribution is attributed to enhanced trap-mediated nonradiative deactivation at the edges compared to the central region of the microdisks. Our results, which unambiguously establish the PL of these Cs₄PbBr₆ and suggest its possible origin, brighten the potential of these materials in photon-emitting applications

Synchronous double C–N bond formation via C–H activation for a novel synthetic route to phenazine

A novel synthetic strategy for phenazine formation is reported following self-coupling of anilines by Pd–Ag binary nanocluster-catalysed synchronous double C–N bond formation via non-radical mode of ortho-aryl C–H activation

Highly efficient energy transfer from a water soluble zinc silver indium sulphide quantum dot to organic J-aggregates

The present work has been carried out with the aim to design and develop an efficient light harvesting inorganic-organic hybrid nanoscale material by employing a less toxic, environment friendly inorganic substance and also to understand the mechanism of inter-particle electronic interaction between the inorganic and organic components of the nanomaterial. Specifically, the inorganic-organic hybrid associate has been made by integrating water soluble semiconductor (zinc-silver-indium-sulfide (ZAIS)) QDs and organic J-aggregates of a cyanine dye (S2165). The fabrication of the present nano-hybrid system has been achievedviaelectrostatically driven self-assembly of organic dyes over ZAIS QDs. The interaction between QD and J-aggregates has been investigated by using steady state and time resolved fluorescence measurements. Zeta potential measurements have also been performed to understand the role of electrostatic interaction and thermodynamic feasibility of the association process. The investigations have revealed that the energy transfer (ET) process between QD and J-aggregates was mediated through a dipole-dipole mechanism. Interestingly, data analysis based on Förster theory has further revealed that the ET from QD to J-aggregates is very high, indicating efficient electronic coupling between the inorganic QD and the organic J-aggregates. Zeta potential measurements and thermodynamic calculations have demonstrated that the interaction between QD and organic dye is electrostatically driven and the association of organic dyes over QDs is thermodynamically feasible. The outcome of the present study is expected to be helpful in designing efficient nanoscale light harvesting devices. Additionally, fluorescence microscopy and toxicity studies on the QDs have also shown their suitability for biological applications

Boosting the Photoluminescence of CsPbX₃ (X = Cl, Br, I) Perovskite Nanocrystals Covering a Wide Wavelength Range by Postsynthetic Treatment with Tetrafluoroborate Salts

Boosting the Photoluminescence of CsPbX₃ (X = Cl, Br, I) Perovskite Nanocrystals Covering a Wide Wavelength Range by Postsynthetic Treatment with Tetrafluoroborate Salt

The palladium and copper contrast: a twist to products of different chemotypes and altered mechanistic pathways

A novel contrast in palladium and copper catalysis is revealed to form products of different chemotypes resulting in a phenazine to azoarene twist through an altered mechanistic pathway (from non-radical C–H activation mode of C–N coupling to radical N–N coupling) during the oxidative self-coupling of anilines catalysed by Pd–Ag and Cu–Ag nanoclusters

Synthesis and X-ray structure of a new zinc(II) coordination polymer: interaction with DNA and double stranded RNA and elucidation of the molecular aspects of the binding to bovine serum albumin

Synthesis and characterization of [Zn(4-Me-5-CHOIm)2(HCOO)](ClO4) complex and binding with nucleic acids and BSA has been explored by different biophysical techniques with the combination of isothermal titration calorimetry (ITC).</p

Synergistic dual activation catalysis by palladium nanoparticles for epoxide ring opening with phenols

Synergistic dual activation catalysis has been devised for epoxide phenolysis wherein palladium nanoparticles induce electrophilic activation via coordination with the epoxide oxygen followed by nucleophilic activation through anion–π;interaction with the aromatic ring of the phenol, and water (reaction medium) also renders assistance through ‘epoxide–phenol’ dual activation