Preparation and Instability of Nanocrystalline Cuprous Nitride

Low-dimensional cuprous nitride (Cu3N) was synthesized by nitridation (ammonolysis) of cuprous oxide (Cu2O) nanocrystals using either ammonia (NH3) or urea (H2NCONH2) as the nitrogen source. The resulting nanocrystalline Cu3N spontaneously decomposes to nanocrystalline CuO in the presence of both water and oxygen from air at room temperature. Ammonia was produced in 60% chemical yield during Cu3N decomposition, as measured using the colorimetric indophenol method. Because Cu3N decomposition requires H2O and produces substoichiometric amounts of NH3\u3e, we conclude that this reaction proceeds through a complex stoichiometry that involves the concomitant release of both N2 and NH3. This is a thermodynamically unfavorable outcome, strongly indicating that H2O (and thus NH3 production) facilitate the kinetics of the reaction by lowering the energy barrier for Cu3N decomposition. The three different Cu2O, Cu3N, and CuO nanocrystalline phases were characterized by a combination of optical absorption, powder X-ray diffraction, transmission electron microscopy, and electronic density of states obtained from electronic structure calculations on the bulk solids. The relative ease of interconversion between these interesting and inexpensive materials bears possible implications for catalytic and optoelectronic applications

From evolutionary computation to the evolution of things

Evolution has provided a source of inspiration for algorithm designers since the birth of computers. The resulting field, evolutionary computation, has been successful in solving engineering tasks ranging in outlook from the molecular to the astronomical. Today, the field is entering a new phase as evolutionary algorithms that take place in hardware are developed, opening up new avenues towards autonomous machines that can adapt to their environment. We discuss how evolutionary computation compares with natural evolution and what its benefits are relative to other computing approaches, and we introduce the emerging area of artificial evolution in physical systems

Strategy for large???scale monolithic Perovskite/Silicon tandem solar cell: A review of recent progress

For any solar cell technology to reach the final mass-production/commercialization stage, it must meet all technological, economic, and social criteria such as high efficiency, large-area scalability, long-term stability, price competitiveness, and environmental friendliness of constituent materials. Until now, various solar cell technologies have been proposed and investigated, but only crystalline silicon, CdTe, and CIGS technologies have overcome the threshold of mass-production/commercialization. Recently, a perovskite/silicon (PVK/Si) tandem solar cell technology with high efficiency of 29.1% has been reported, which exceeds the theoretical limit of single-junction solar cells as well as the efficiency of stand-alone silicon or perovskite solar cells. The International Technology Roadmap for Photovoltaics (ITRPV) predicts that silicon-based tandem solar cells will account for about 5% market share in 2029 and among various candidates, the combination of silicon and perovskite is the most likely scenario. Here, we classify and review the PVK/Si tandem solar cell technology in terms of homo- and hetero-junction silicon solar cells, the doping type of the bottom silicon cell, and the corresponding so-called normal and inverted structure of the top perovskite cell, along with mechanical and monolithic tandemization schemes. In particular, we review and discuss the recent advances in manufacturing top perovskite cells using solution and vacuum deposition technology for large-area scalability and specific issues of recombination layers and top transparent electrodes for large-area PVK/Si tandem solar cells, which are indispensable for the final commercialization of tandem solar cells

Femtosecond tunneling of polarons in Pb5Cr3F19

The complex dielectric constant/ac electrical conductivity was investigated as a function of frequency and temperature in Pb5Cr3F19. The system undergoes a ferroelectric phase transition at higher temperatures. At lower temperatures the real part of the complex ac electric conductivity was found to follow the universal dielectric response (UDR) σ′ ∝ νs, typical for hopping or tunneling of localized charge carriers. A detailed analysis of the temperature dependence of the UDR parameter s in terms of the theoretical model for tunneling of small polarons revealed that, at low temperatures, this mechanism governs the charge transport in Pb5Cr3F19. The value of the inverse attempt frequency τ0 indicates the femtosecond tunneling of polarons in the system similar to the Büttiker–Landauer transversal time

Polarons in magnetoelectric K

The ac electrical conductivity of magnetoelectric K3Fe5F15 was investigated as a function of frequency and temperature. While at higher temperatures charge transport is governed by a thermally activated process, at lower temperatures the real part of the complex ac electric conductivity was found to follow the universal dielectric response $\sigma^\prime\propto\nu^{s}$, being typical for hopping or tunnelling of localized charge carriers. A detailed analysis of the temperature dependence of the UDR parameter s in terms of the theoretical model for tunnelling of small polarons revealed that, below 80 K, this mechanism governs the charge transport in the K3Fe5F15 magnetoelectric fluoride system

Reusable Au/Pd-coated chestnut-like copper oxide SERS substrates with ultra-fast self-recovery

Reliable and reusable plasmonic substrates are crucial for the development of biosensing applications using surface-enhanced Raman scattering (SERS), as they can provide unique advantages for ultrafast and accurate single-molecule recognition of different species. These properties are unrevealed in this paper, where thermally annealed cupric CuO and cuprous oxide Cu2O heterostructures were used as templates for highly stable nanotextured surfaces and design of robust 3D plasmonic biochips. Differently tailored nano/micro-roughness provided outstanding light trapping abilities that lead to significant SERS performance improvement. It was found that Cu2O chestnut-like substrate activated with 80 nm Au/Pd alloy film reveals impressive 3.7-fold Raman signal increment in respect to grainy-like structure and about twice larger amplification than that of nanowires enriched platform decorated in the same manner. Large enhancement factor AEF ~5 × 105 of a chestnut-like Au/Pd@/Cu2O chip allows adding it up to the list of the most effective oxide-based plasmonic substrates. Moreover, the substrate shows unprecedented durability during repetitive plasma-cleaning, demonstrating a remarkable 100 self-recovery in less than 1 min, accompanied by virtually no thickness degradation of the plasmonic layer. © 2020 Elsevier B.V

Optical Optimization of Perovskite Solar Cell Structure for Maximum Current Collection

This paper was presented at the E-MRS Spring Meeting 2016 Symposium T - Advanced materials and characterization techniques for solar cells III, 2-6 May 2016, Lille, France. This is an Open Access Article. It is published by Elsevier under the Creative Commons Attribution Non Commercial-No Derivatives 4.0 Unported Licence (CC BY-NC-ND). Full details of this licence are available at: http://creativecommons.org/licenses/by-nc-nd/4.0/High conversion efficiency has been recently demonstrated for Perovskite thin film photovoltaic devices. Perovskite thin film solar cells are multilayer opto-electrical structures in which light interference occurs. This phenomenon can be used to maximise the light transmission into the absorber material and increase the device efficiency. Fine tuning of the layer thicknesses within the stack can be used to control interference at the interfaces. Optical reflection losses can be reduced by achieving destructive interference within the structure of the cell. The light transmission to the Perovskite absorber of a thin film solar cell on a fluorine doped tin oxide transparent conductor has been modelled using the transfer matrix method. Alternative transparent conductor materials have been also investigated including AZO and ITO. The modelling showed that replacing FTO with ITO could increase the photocurrent by as much as 4.5%. The gain can be further increased to 6.5% by using AZO as the TCO material. Fine tuning of the TiO2 layer thickness can increase the current density by 0.3%. Furthermore, the current density of a Perovskite solar cell can be increased by application of a multilayer anti-reflective coating by another 3.5%. Optical optimisation of the stack design offers a significant increase in conversion efficiency