Cathodoluminescence hyperspectral imaging on the nanometre scale

Extending cathodoluminescence microscopy into the hyperspectral imaging mode brings significant benefits to an already powerful nano-scale characterization tool. In this paper, we give an introduction to the technique, and illustrate its potential with examples of its application to both semiconducting and plasmonic nanostructures

Wide-bandgap halide perovskites for indoor photovoltaics

LJ acknowledges the funding through the UKRI-Future Leaders Fellowship (MR/T022094/1).Indoor photovoltaics (IPVs) are receiving great research attention recently due to their projected application in the huge technology field of Internet of Things (IoT). Among the various existing photovoltaic technologies such as silicon, Cadmium Telluride (CdTe), Copper Indium Gallium Selenide (CIGS), organic photovoltaics, and halide perovskites, the latter are identified as the most promising for indoor light harvesting. This suitability is mainly due to its composition tuning adaptability to engineer the bandgap to match the indoor light spectrum and exceptional optoelectronic properties. Here, in this review, we are summarizing the state-of-the-art research efforts on halide perovskite-based indoor photovoltaics, the effect of composition tuning, and the selection of various functional layer and device architecture onto their power conversion efficiency. We also highlight some of the challenges to be addressed before these halide perovskite IPVs are commercialized.Publisher PDFPeer reviewe

Cross-sectional and plan-view cathodoluminescence of GaN partially coalesced above a nanocolumn array

The optical properties of GaN layers coalesced above an array of nanocolumns have important consequences for advanced optoelectronic devices. GaN nanocolumns coalesced using a nanoscale epitaxial overgrowth technique have been investigated by high resolution cathodoluminescence (CL) hyperspectral imaging. Plan-view microscopy reveals partially coalesced GaN layers with a sub-μm scale domain structure and distinct grain boundaries, which is mapped using CL spectroscopy showing high strain at the grain boundaries. Cross-sectional areas spanning the partially coalesced GaN and underlying nanocolumns are mapped using CL, revealing that the GaN bandedge peak shifts by about 25 meV across the partially coalesced layer of ∼2 μm thick. The GaN above the nanocolumns remains under tensile strain, probably due to Si out-diffusion from the mask or substrate. The cross-sectional data show how this strain is reduced towards the surface of the partially coalesced layer, possibly due to misalignment between adjacent partially coalesced regions

Manual de capacitación en técnicas activas

PDFLas denominadas Tecnologías de la Información y las Comunicaciones (TIC`S) ocupan un lugar central en la sociedad y en la economía desde finales del siglo XX, con una importancia creciente. Comprenden un conjunto de tecnologías que permiten la adquisición, producción, almacenamiento, tratamiento, comunicación, registro y presentación de informaciones, en forma de voz, imágenes y datos contenidos en señales de naturaleza acústica, óptica o electromagnética. Este proyecto se refiere al uso de las TIC’S para la enseñanza de Matemática a los/as estudiantes de la carrera de Educación Básica de la Facultad de Filosofía. El principal propósito es diagnosticar las causas de la falta de aplicación de las TIC’S en la enseñanza, para motivar la actualización tecnológica y optimizar y mejorar la calidad de la educación en esta área neurálgica, por el número de fracasos escolares y los bajos resultados en la evaluación de logros. Este trabajo hace referencia al problema y expone la ubicación del mismo en el contexto del uso de la Tecnología en la carrera. En el marco teórico se define a las TIC’S, y se destaca su importancia en la didáctica de Matemática con la aplicación de las TIC’S como herramienta básica en el aula, la enorme potencialidad de apoyar los procesos de enseñanza y aprendizaje. La metodología y procedimientos de investigación junto con el análisis de los resultados, de las encuestas a laboratoristas informáticos, estudiantes y la entrevista al experto diseñador de software informáticos aplicado al área de Matemática. Sobre la base de los resultados de investigación se propone el diseño de un Manual de Capacitación en Técnicas Activas con la utilización de las TIC’S, para que los docentes obtengan los fundamentos teóricos y herramientas para la aplicación de tecnología educativa en la enseñanza de Matemática.The denominated Technologies of the Information and the Communications (TIC`S) occupy a important place in the society and in the economy from final of the XX century, with a growing importance. They are part from a group of technologies that allow the acquisition, production, storage, treatment, communication, registration and presentation of information, in a voice way, images and data in signs of acoustic nature, optics or electromagnetic. This project refers to the use of the TIC'S for the teaching of Mathematical to the students of Basic Education career form the Faculty of Philosophy. The main purpose is to diagnose the causes of the lack of application of the TIC'S in the teaching, to motivate the technological upgrade and to optimize and improve the quality of the education in this area, for the number of school failures and low results in the evaluation of achievements. This work makes reference to the problem and it exposes the location of itself in the context to use the Technology in the career. The theoretical mark is defined to the TIC'S, and it stands out their importance in the didactics of Mathematical with the application of the TIC'S like basic tool in the classroom, the enormous potentiality of supporting the teaching processes and learning. The methodology and investigation procedures with the analysis of the results, from the surveys to computer lab people, students and the interview to the expert designer of software computer specialist applied to the area of Mathematical. On the base of the investigation results it intends the design of a Manual of Training in Active Techniques with the use of the TIC'S, so that the professors obtain the theoretical foundations and tools for the application of educational technology in the teaching of Mathematical

Piezoelectric charge coefficient of halide perovskites

Funding: LKJ acknowledges funding from UKRI-FLF through MR/T022094/1.Halide perovskites are an emerging family of piezoelectric and ferroelectric materials. These materials can exist in bulk, single-crystal, and thin-film forms. In this article, we review the piezoelectric charge coefficient (dij) of single crystals, thin films, and dimension-tuned halide perovskites based on different measurement methods. Our study finds that the (dij) coefficient of the bulk and single-crystal samples is mainly measured using the quasi-static (Berlincourt) method, though the piezoforce microscopy (PFM) method is also heavily used. In the case of thin-film samples, the (dij) coefficient is dominantly measured by the PFM technique. The reported values of dij coefficients of halide perovskites are comparable and even better in some cases compared to existing materials such as PZT and PVDF. Finally, we discuss the promising emergence of quasi-static methods for thin-film samples as well.Peer reviewe

Analisis Pengaruh Kebisingan, Beban Kerja, Konflik Keluarga – Pekerja Terhadap Stres Kerja Karyawan Cv. Anugrah Cipta Perkasa Pati

Stres kerja karyawan sangatlah berperan penting dalam suatu keberlangsungan perusahaan. Stres kerja karyawan akan muncul apabila seseorang mengalami kebisingan, beban kerja, dan konflik keluarga - pekerja sebagai salah satu faktor yang mempengaruhinya. CV. Anugrah Cipta Perkasa sebagai lokasi penelitian dengan jumlah responden 86 orang karyawan dengan metode purposive sampling. Tehnik analisis data yang digunakan untuk menguji hipotesis adalah analisis regresi untuk mengetahui pengaruh positif secara parsialnya maupun berganda serta menentukan variabel yang lebih besar mempengaruhi stres kerja karyawan. Hasil analisis diketahui bahwa variabel kebisingan, beban kerja dan konflik keluarga - pekerja berpengaruh positif dan signifikan secara parsial maupun berganda. Ini terlihat dari nilai pada variabel kebisingan (X1) nilai t hitung nya sebesar 2.884, variabel beban kerja (X2) nilai t hitung nya sebesar 2.611, variabel konflik keluarga – pekerja (X3) nilai t hitung nya sebesar 2.836, seluruhnya memiliki nilai t hitung> t tabel sebesar 1.663 dan memiliki prob. Sig lebih kecil dari 0.05. Dan nilai F hitung> F tabel (9.229> 2.720) dan tingkat signifikansi 0,000 < 0,05 maka dinyatakan bahwa variabel kebisingan, beban kerja dan konflik keluarga - pekerja secara simultan mempengaruhi variabel stres kerja. Nilai Adjusted R Square adalah 0,225, hal ini berarti 22,5% variasi stres kerja (Y) dapat dijelaskan kebisingan, beban kerja dan konflik keluarga - pekerja

High-resolution cathodoluminescence hyperspectral imaging of nitride nanostructures

Hyperspectral cathodoluminescence imaging provides spectrally and spatially resolved information on luminescent materials within a single dataset. Pushing the technique toward its ultimate nanoscale spatial limit, while at the same time spectrally dispersing the collected light before detection, increases the challenge of generating low-noise images. This article describes aspects of the instrumentation, and in particular data treatment methods, which address this problem. The methods are demonstrated by applying them to the analysis of nanoscale defect features and fabricated nanostructures in III-nitride-based materials

Interface limited hole extraction from methylammonium lead iodide films

Small solar cells based on metal halide perovskites have shown a tremendous increase in efficiency in recent years. These huge strides in device performance make it important to understand processes such as accumulation and extraction of charge carriers to better address the scalability and stability challenges which have not been solved yet. In most studies to date it is unclear whether the limiting factor of charge extraction is charge transport in the bulk of the perovskite or transfer across the interface with the charge extracting layer, owing largely to the inaccessibility of buried interfaces. Separating bulk and interfacial effects on charge extraction can help the search for new charge extracting materials, improve understanding of charge transport in active layer materials and help optimise device performance; not only in the laboratory setting but also for commercial production. Here we present a method to unambiguously distinguish between bulk and interface effects on charge extraction dynamics which is based on time-resolved photoluminescence with different excitation density profiles. We use this method to study charge extraction from solution-deposited CH3NH3PbI3 films to NiO and PEDOT:PSS layers. We find that NiO shows faster hole extraction than PEDOT:PSS from the 300 nm thick perovskite film on the time scale of 300 ps which is independent of charge carrier density in the region of 1016–1017 cm−3. The interface with NiO is found to only slightly limit charge extraction rate at charge densities exceeding 1016 cm−3 as the extraction rate is fast and does not decrease with time. This is in contrast to PEDOT:PSS where we find the charge extraction rate to be slower, decreasing with time and dependent on charge density in the region 1016–1017 cm−3 which we interpret as charge accumulation at the interface. Hence we find that charge extraction is severely limited by the interface with PEDOT:PSS. These findings are confirmed by transient absorption spectroscopy. A hole diffusion coefficient of D = (2.2 ± 0.5) cm2 s−1 was determined in the perovskite film that is independent of charge density. This indicates a band-like hole transport regime, not observed for solution processed films before. Our findings stress the importance of interface optimization in devices based on perovskite active layers as there is still room for improvement of the hole extraction rate even in the case of the superior NiO layer

Hysteresis in hybrid perovskite indoor photovoltaics

L.K.J. acknowledges funding from UKRI-FLF through grant no MR/T022094/1.Halide perovskite indoor photovoltaics (PV) are a viable solution to autonomously power the billions of sensors in the huge technology field of the Internet of Things. However, there exists a knowledge gap in the hysteresis behaviour of these photovoltaic devices under indoor lighting conditions. The present work is the first experimental study dedicated to exploring the degree of hysteresis in halide perovskite indoor photovoltaic devices by carrying out both transient J-V scan and steady state maximum power point tracking (MPPT) measurements. Dependence of hysteresis on device architecture, selection of electron transporting layers and the composition of the perovskite photoactive layers were investigated. Under indoor illumination, the p-i-n MAPbI3-based devices show consistently high power conversion efficiency (PCE) (stabilized PCE) of greater than 30% and negligible hysteresis behaviour, whereas the n-i-p MAPbI3 devices show poor performance (stabilized PCE ∼ 15%) with pronounced hysteresis effect. Our study also reveals that the n-i-p triple cation perovskite devices are more promising (stabilized PCE ∼ 25%) for indoor PV compared to n-i-p MAPbI3 due to their suppressed ion migration effects. It was observed that the divergence of the PCE values estimated from the J-V scan measurements, and the maximum power point tracking method is higher under indoor illumination compared to 1 Sun, and hence for halide perovskite-based indoor PV, the PCE from the MPPT measurements should be prioritized over the J-V scan measurements. The results from our study suggest the following approaches for maximizing the steady state PCE from halide perovskite indoor PV: (i) select perovskite active layer composition with suppressed ion migration effects (such as Cs-containing triple cation perovskites) and (ii) for the perovskite composition such as MAPbI3, where the ion migration is very active, p-i-n architecture with organic charge transport layers is beneficial over the n-i-p architecture with conventional metal oxides (such as TiO2, SnO2) as charge transport layers. This article is part of the theme issue 'Developing resilient energy systems'.Publisher PDFPeer reviewe