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The present invention provides for a composition comprising an inorganic scintillator comprising an optionally lanthanide-doped barium mixed halide, useful for detecting nuclear material.
This disclosure provides systems, methods, and apparatus related to heterojunctions in halide perovskite nanostructures. In one aspect, a nanostructure comprises a first region and a second region. The first region comprises ABX3, with A being selected from a group consisting of Cs and Rb, with B being selected from a group consisting of Sn and Pb, and with X being selected from a group consisting of Br, Cl, and Br and Cl. The second region comprises ABY3, with Y being selected from a group consisting of Br, I, and Br and I. Compositions of the first region of the nanostructure and the second region of the nanostructure are different.
A method of forming lead halide perovskite crystals in a solvent. The perovskite is form by solution processing of an organic and inorganic precursor in a polar protic solvent.
Over the past decade, metal halide perovskites (MHPs) have emerged as a promising materials platform for high-efficiency solar cells and low-cost optoelectronics. However, there are challenges that frustrate the large-scale manufacturing of MHP devices, including difficulty in controlling film composition, interface formation and their device instability under ambient conditions. Vapor processing offers an attractive path to manufacturability, while also opening the door to new opportunities in device design that could favorably impact ultrahigh efficiency tandem solar cells or overall stability. Emphasis here is on the use of an alternate processing methodology, vapor transport deposition (VTD), to deposit the MHP layer. In experimental work, we found that our deposition system had significant run-to-run variations in film thickness and composition. To understand and resolve these issues, we use COMSOL Multiphysics software to model the precursor deposition rate numerically, trying to guide the broad range of parameters in the system. The result can be matched with experimental data and provides insight into system hydrodynamics and molar transport effects. Finally, we show that chamber pressure is a key factor to scale up the VTD technique.
The present invention provides for a composition comprising an inorganic scintillator comprising an optionally lanthanide-doped cesium barium halide, useful for detecting nuclear material.
Metal halide perovskite (MHP) photovoltaics (PV) are a potentially transformational next-generation energy technology. These materials have remarkable and tunable physical properties that enable a range of process approaches to produce high-efficiency devices. NREL efforts address both basic material and device-level considerations to advance the state of the art in MHP PV and accelerate its path to market.
Metal halide perovskite semiconductors are widely used in emerging photovoltaic (PV) products. These semiconductors benefit from low-cost processing and unusual electronic characteristics that lead to high efficiency. Researchers at the National Laboratory of the Rockies (NLR) address material, device-level, and module-level considerations to help bring perovskite PV to market.
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Liumogen and recent work on sodium salicylate
Here, a comprehensive study of the exciton fine structure (EFS) is presented in 2D-phenethylammonium lead iodide films using magnetic field-induced polarization of photoluminescence (PL) in both Faraday and Voigt configurations at fields up to 25 Tesla. Three exciton bands are identified in the PL spectrum associated with bound, dark, and bright excitons, respectively. Under a high magnetic field in Faraday/Voigt configuration, large field-induced circular/linear polarization is observed in the PL band related to the dark exciton, which is magnetically activated. Furthermore, it is found that the dark exciton has an anomalous field-induced circular polarization, which cannot be explained by the classical Boltzmann distribution of spin-polarized species. These findings are well explained by an effective mass model that includes exchange terms unique to the monoclinic symmetry as a perturbation of the EFS in the approximate tetragonal symmetry. It is also confirmed that the field-induced linear polarization is sensitive to the monoclinic exchange term, whereas the field-induced circular polarization is immune to such term.
Semiconductor nanoplatelets (NPLs), with their large exciton binding energy, narrow photoluminescence (PL), and absence of dielectric screening for photons emitted normal to the NPL surface, could be expected to become the fastest luminophores amongst all colloidal nanostructures. However, super-fast emission is suppressed by a dark (optically passive) exciton ground state, substantially split from a higher-lying bright (optically active) state. Here, the exciton fine structure in 2-8 monolayer (ML) thick Cs n - 1 Pb n Br 3n + 1 NPLs is revealed by merging temperature-resolved PL spectra and time-resolved PL decay with an effective mass model taking quantum confinement and dielectric confinement anisotropy into account. This approach exposes a thickness-dependent bright-dark exciton splitting reaching 32.3 meV for the 2 ML NPLs. The model also reveals a 5-16 meV splitting of the bright exciton states with transition dipoles polarized parallel and perpendicular to the NPL surfaces, the order of which is reversed for the thinnest NPLs, as confirmed by TR-PL measurements. Accordingly, the individual bright states must be taken into account, while the dark exciton state strongly affects the optical properties of the thinnest NPLs even at room temperature. Significantly, the derived model can be generalized for any isotropically or anisotropically confined nanostructure.
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The high-temperature (high-T) phase of cesium lead iodide (CsPbI 3 ) presents great promise for photovoltaic applications; however, exposure to ambient moisture at room temperature transforms it into its less-desirable low-temperature (low-T) phase with a larger band gap. While there have been theoretical predictions on the influence of moisture level on the phase transformation kinetics, the corresponding quantitative experimental evidence has remained limited. Tracking CsPbI 3 phase transformation under controlled relative humidity (RH), we find that rising RH increases the nucleation rate of low-T CsPbI 3 exponentially, but has a weak effect on its growth. The overall transformation is nucleation limited, with higher RH leading to a lower nucleation barrier. Finally, we find that heating between 40°C and 80°C facilitates water desorption and suppresses phase transformation. Our findings elucidate the relationship between moisture and the phase energetics of CsPbI 3 , which can serve as references for thin film applications of CsPbI 3 and future designs of stable photovoltaics systems.
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Methylammonium lead iodide (MAPbI 3-x Cl x ) thin films were synthesized using chemical vapor deposition. Temperature-dependent grazing incidence synchrotron-based X-ray diffraction measurements confirm that the structure of MAP-bI 3-x Cl x , where Cl acts more like a dopant, remains throughout in the tetragonal phase in the temperature range of 20-300 K. Here these studies are further correlated with temperature-dependent photo-luminescence (PL) studies. The PL peak energy monotonically increases with temperature, suggestive of a single-phase behavior. Resistance measurements conducted as a function of temperature show an absence of inflection points, suggesting uniformity in its phase. Between 200 and 325 K, the resistance remains a constant.