61 Search Results

Chiral perovskites are semiconductors with broken mirror symmetries. Their photo responses are often constrained in the UV range. In this work, we demonstrate that doping 2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane in the chiral perovskite matrix introduces a visible light absorption feature through the emerging charge-transfer electronic states. These charge-transfer states exhibits circular dichroism inherited from the chiral host, indicating effective chirality transfer from host to guest component via electronic coupling. Quantum-chemical modeling identifies a strong wave function overlap between an electron and a hole of the guest-host in a closely packed crystal configuration promoting the charge transfer state’s optical activity. We further integrate themore » doped chiral perovskite film into photodetectors and demonstrate a selective detection of circularly polarized light in both UV and visible regions. Our results suggest a universal approach of introducing visible photo absorption states to the chiral matrix to broaden the optical active range while enhancing the electrical conductivity.« less

In this report, the role that a high-boiling-point solvent type plays on the nucleation and growth, morphology, and crystal-phase transformation of cesium lead bromide nanocrystals (CsPbBr₃) is studied. The CsPbBr₃ products were compared between a one-pot growth mechanism at room temperature (RT) versus a hot-injection mechanism (HI) control using dibenzyl ether (DBE), diphenyl ether (DPE), dioctyl ether (DOE), or 1- octadecene (ODE). The coordination between these solvents and the PbBr₂ salt precursors resulted in different plumbate [PbSBr_n]²⁻ⁿ precursors being formed. The S-to-Pb²⁺ coordination within [PbSBr_n]²⁻ⁿ was probed by UV−vis and solvent-phase ²⁰⁷Pb NMR, both of which showed considerable coordination betweenmore » [PbSBr_n]²⁻ⁿ and the π-rich DBE and DPE, whose reactivity affected CsPbBr₃ growth. The effect was more pronounced for CsPbBr₃ prepared via RT, where the morphology was tunable, with π-rich solvents producing thin rod-like CsPbB^r3 with a blue emission, compared to the green-emitting thicker platelets formed via HI. While XRD showed crystalline products for both RT and HI, with orthorhombic and cubic forms, respectively, the RT products had considerable surface defects, as was indicated by lower quantum yields, and to understand this the photoluminescent lifetimes were measured by time-correlated single photon counting.« less

The growth pattern of atomically precise nanoclusters (NCs) is of fundamental interest, and the structural effect on their photoluminescence (PL) is important owing to their PL in the second near-infrared (NIR-II) range (900–1700 nm optoelectronically or 1000–1700 nm biologically) that holds great promise for optoelectronic and biomedical applications. Because of the small energy gaps required for NIR-II emission, the PL performance of NIR-II luminophores is largely limited by nonradiative processes. In this work, we discovered a Au₇₆(p-MBT)₄₂ (Au₇₆) (p-MBTH = p-methylbenzenethiol) nanocluster featuring a face-centered cubic (fcc) core in a square shape (edge length: 1 nm). This square quantum plateletmore » can be viewed as a side-facet (010) growth of the Au₅₂(p-MBT)₃₂ (Au₅₂) rod, as opposed to the (001) facet growth. We found that Au₇₆ exhibits bright emission centered at 970 nm with a PL quantum yield (PLQY) of 30% in solution under ambient conditions, which can be further enhanced to 40% when the solution is deaerated. X-ray crystallography analysis coupled with time-resolved spectroscopy revealed that the nearly doubled PLQY compared to Au₅₂ (18.3%) was resulted from shorter Au–Au bond lengths in Au₇₆ (average 2.835 Å) than that in Au₅₂ (3.04 Å). This work provides important insights into the design of highly luminescent NCs, which are promising for photovoltaics, photocatalysis, and optoelectronic applications.« less

Metal halides are an important class of optoelectronic materials combining exceptional optical and electronic properties. An inherent advantage of metal halides is their solution synthesis and processability, which render them as low-cost and environmentally friendly materials for a range of applications from photovoltaics and photodetection to solid-state lighting (SSL). Here, in this study, we synthesized three previously unreported lead-free organic–inorganic hybrid copper halides: (OA)₄CuX₅ (X = Br, I; OA⁺ = C₈H₁₇NH³⁺, n-octylammonium cation) and (HA)₂CuI₃ (HA⁺ = C₆H₁₃NH₃⁺, n-hexylammonium cation), all of which exhibit broadband emissions arising from self-trapped excitons (STEs). Among these compounds, (OA)₄CuI₅ demonstrates tunable dual-band white-light emissionmore » with a high color rendering index value of 91 at room temperature. Temperature-dependent photoluminescence measurements and first-principles calculations reveal distinct behaviors between the two emission states in (OA)₄CuI₅. These findings highlight the potential of copper halide compounds for optoelectronic applications, particularly in the development of environmentally friendly solid-state lighting technologies.« less

Solution-processed light-emitting diodes based on non-toxic copper–iodide hybrids are a compelling solution for efficient and stable deep-blue lighting, owing to their tunability, high photoluminescence efficiency and environmental sustainability. Here we present a hybrid copper–iodide that shows near-unity photoluminescence quantum yield (99.6%) with an emission wavelength of 449 nm and colour coordinates (0.147, 0.087), alongside its emission mechanism and charge transport characteristics. Here, we use the thin film of this hybrid as the sole active emissive layer to fabricate deep-blue light-emitting diodes and subsequently enhance the device performance through a dual interfacial hydrogen-bond passivation strategy. This synergetic surface modification approach, integratingmore » a hydrogen-bond-acceptor self-assembled monolayer with an ultrathin polymethyl methacrylate capping layer, effectively passivates both heterojunctions of the copper–iodide hybrid emissive layer and optimizes charge injections. We achieve a maximum external quantum efficiency of 12.57%, a maximum luminance of 3,970.30 cd m⁻² with colour coordinates (0.147, 0.091) and an excellent operational stability (half-lifetime) of 204 hours under ambient conditions. We further showcase a large-area device of 4 cm² that maintains high efficiency. Our findings reveal the potential of copper–iodide-based hybrid materials for applications in solid-state lighting and display technologies, offering a versatile strategy for enhancing device performances.« less

2D-on-3D (2D/3D) perovskite heterostructures with engineered energy landscapes offer the potential to realize efficient and stable inverted solar cells. However, managing the energy landscape using 2D perovskites with thicker inorganic layers n > 1 necessitates the usage of the chemically unstable methylammonium MA⁺. Here, we synthesized formamidinium (FA)-rich and pure-FA n = 3 Ruddlesden-Popper (RPP) and Dion-Jacobson perovskite (DJP) single crystals by identifying ligands with suitably lattice-matched organic and inorganic components of the 2D lattice. These crystals were translated onto 3D perovskites as capping layers, forming 2D/3D hetero-bilayers (HBs). Degradation studies revealed that HBs with butylammonium-based RPPs as capping layersmore » rapidly phase segregate into non-perovskites under combined extrinsic stressors, compromising the underlying 3D layer, whereas FA-rich DJPs based on 3-aminomethylpiperidine retain their phase stability. The DJP HBs also possess a favorable energy landscape and electron transport at the 2D/3D interface, enabling inverted solar cells with a champion PCE of 25.33% and remarkable stability.« less

The near-infrared (NIR) emission of silicon–germanium alloy nanocrystals (SiGe NCs) was sensitized by heterostructuring with a quasi two-dimensional (Q-2D) perovskite (CsPbBr₃ blended with butylammonium bromide (BABr)). Colloidal SiGe NCs were synthesized by using a nonthermal plasma method with chloride precursors. As-synthesized SiGe NCs showed no detectable photoluminescence (PL). Embedding the SiGe NCs within the perovskite matrix via spin coating led to a heterostructure exhibiting dual emissions: green emission at 520 nm from the perovskite and NIR emission at 1035 nm from the SiGe NCs. Time-integrated and resolved PL measurements and transient absorption spectroscopy revealed energy transfer from the perovskite tomore » the SiGe NCs, which sensitized the NIR emission from the SiGe NCs and quenched the green PL for the perovskite. These results demonstrate that Ge alloying can effectively tune the bandgap of Si NCs and highlight the feasibility of heterostructuring perovskites and photoluminescent NCs to enhance or activate their PL. In conclusion, this approach broadens their potential applications in the NIR region.« less

Broadband emissions in a series of alkali chlorides are achieved by doping NaCl, KCl, and RbCl with Sb ³⁺ .

We report the synthesis and programmed self-assembly of m-phenylene vinylene (m-PPV) derivatives containing amino acid functional groups. These derivatives form highly fluorescent nanofibres through hydrogen bonding, rather than π–π stacking. Systematic investigation of tyrosine-based derivatives reveals the critical role of lateral and vertical hydrogen bonding sites in forming uniform, high-aspect-ratio nanofibres, as confirmed by cryo-TEM and SEM (diameters 2–3 nm, lengths > 20 μm). Chiral centres promoted helical nanofibres, while achiral oligomers formed straight fibres. Our study demonstrates the ability to form large-area, homogeneous straight and helical nanofibres with a high aspect ratio and increased melting point from 185 °Cmore » to 209.4 °C. Photophysical studies showed thickness-dependent fluorescence lifetimes, attributed to self-quenching. This work enhances the understanding of structure–property relationships in supramolecular assemblies and offers a new design strategy for biomimetic nanomaterials.« less

Here, the presence of poly- and perfluoroalkyl substances (PFAS) in the environment is associated with adverse health effects but measuring PFAS is challenging due to the associated high cost and technical complexities of the analysis. Here, the reactivity of atomically precise metal-oxo clusters is reported and the foundation for their use is provided as fluorescent nanosensors for PFAS detection. The material comprises crystalline, water soluble, hexanuclear cerium-oxo clusters [Ce₆(µ₃-O)₄(µ₃-OH)₄]¹²⁺ decorated with glycine molecules (Ce-Gly) characterized by fluorescence emission at 353 nm. The Ce-Gly fluorescence is found sensitive to long chain carboxylated PFAS of CF₃–(CF₂)_n –, where n ≥ 6, suchmore » as perfluorooctanoic, perfluorononanoic and perfluorodecanoic acids. This unique reactivity leads to a change in the emission spectra in a concentration dependent manner, enabling PFAS detection through ligand exchange and aggregation-induced emission (AIE) enhancement. No significant cross-reactivity from potentially co-existing species, including sulfonated PFAS, octanoic and dodecanoic acids, humic acid, and inorganic ions is observed. With an optimal concentration of 3.3 µg mL^-1 Ce-Gly, the method demonstrated detection limits of 0.24 ppb for PFOA and 0.4 ppb for PFNA. These findings highlight the potential of fluorescence-based detection strategies utilizing nanoscale probes such as Ce-Gly as fluorescent probes and nanosensors for PFAS.« less