Band gap engineering of hybrid perovskites for solar cells
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This document discusses band gap engineering of hybrid organic-inorganic lead halide perovskites. It describes how the band gap of methylammonium lead iodide bromide perovskites can be tuned between 1.55-2.29 eV by varying the halide composition in the solution during a two-step deposition process. Using a mesoporous scaffold improves the mechanical stability of the perovskite films. Annealing after deposition prevents instant degradation but affects uniform film formation. The goal is to optimize the fabrication process and characterize the resulting perovskite films.
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This document provides an overview of non-conventional machining processes including ultrasonic machining, water jet machining, electro-chemical machining, electro-chemical grinding, and electrical discharge machining. The objective is to make audiences aware of the merits of these non-conventional processes over traditional machining for machining complex, less machinable, or brittle materials in a faster and more economical way using computer-controlled processes with minimal human intervention. An outline and brief description is given for each non-conventional machining technique.
Igneous rocks formaion through chemical weathering
Igneous rocks are generally termed as fire rocks formed either underground or above ground there are two types Intrusive, Extrusive igneous rocks mainly containing high silica content
Cambridge NanoTech Overview
Cambridge NanoTech produces atomic layer deposition (ALD) systems for research and production. Their ALD systems use alternating pulses of precursor gases to deposit thin, conformal films one atomic layer at a time. This allows for precise thickness control and excellent uniformity. Their product line includes thermal and plasma ALD systems suitable for R&D or high-volume manufacturing.
Wafer cleaning
The document discusses wafer cleaning techniques which are the most important step in the wafer fabrication process. It describes various sources of contamination on wafer surfaces like particles, metals, organics and how they can affect device performance. Standard cleaning procedures using wet chemical solutions like SC1, SC2, sulfuric acid mixtures and advanced techniques like megasonic cleaning are explained. The key steps of cleaning, rinsing with deionized water and drying the wafers are outlined. Priming the wafer surface before photoresist coating is also summarized.
Mram
MRAM is a type of non-volatile memory that uses magnetism instead of electricity to store data. It has the potential for unlimited read/write endurance, high speed performance, and lower power consumption compared to other RAM technologies. MRAM uses magnetic tunnel junctions consisting of two ferromagnetic plates separated by an insulator, where one plate's magnetization represents a 1 and the other a 0. Over time, MRAM development has improved switching speed and density, with multi-Mbit demonstration chips produced in the 2000s and research continuing on thermal assisted switching and spin torque transfer to enable smaller geometries.
Sebastiani - Nano-mechanical and microstructural characterization of MS-PVD N...
This document summarizes a presentation on nano-mechanical and microstructural characterization of niobium thin films deposited by magnetron sputtering. Key points discussed include:
- Four niobium coatings were produced by varying the applied bias voltage and substrate material.
- Nanoindentation testing revealed the coatings' hardness is not affected by the substrate at depths less than one tenth the coating thickness.
- Analysis of deformation mechanisms using FIB sectioning showed columnar grain sliding and recrystallization during plastic deformation.
- A thin surface oxide layer of around 10nm was found, which could impact the coatings' superconducting performance.
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Igneous rocks formaion through chemical weathering
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Similar to Band gap engineering of hybrid perovskites for solar cells
Rani
This document describes a project on the formation of PbS thin films using the chemical bath deposition technique. The aims are to deposit PbS thin films using CBD, study the effect of different precursor solutions, and characterize the films using XRD. CBD is described as a low-cost deposition method using controlled chemical reactions. Procedures for depositing PbS films using lead acetate and lead nitrate precursors are provided. XRD results show the films are PbS cubic crystals with grain sizes of 41.9nm and 45.44nm for lead nitrate and acetate, respectively. Conductivity tests show the films are p-type. The effect of varying lead concentration is also studied.
Xiaoxing xi progress in the investigation of mg b2 thin films for srf cavit...
MgB2 thin films grown by hybrid physical-chemical vapor deposition (HPCVD) have been investigated for SRF cavity applications. I will present our recent results of research in three directions: enhancement of Hc1 in thin MgB2 films, large area MgB2 films on Cu, and the effort on coating of RF cavities. By reducing the thickness of the MgB2 film from 300 nm to 100 nm, Hc1(0) increases systematically from 38 mT to about 200 mT in both epitaxial and polycrystalline films. The HPCVD process has been successfully applied on 2” diameter Cu substrate. Both the in-situ and two-step processes have been used for the coating of a 6 GHz cavity. Samples from various locations of the cavity show good superconducting properties. Effort is underway to coat 3 GHz RF cavities.
2021 recent trends on high capacity cathode
The document summarizes recent work on nickel-rich layered oxide cathodes and cobalt-free layered oxide cathodes for lithium-ion batteries.
For nickel-rich NMC811 cathodes, a multi-step synthesis method produced better crystallinity and less cation mixing compared to a one-pot method, as indicated by a higher I003/I104 ratio from XRD. The multi-step NMC811 also showed better capacity retention over 30 cycles.
For cobalt-free NMF111 cathodes, a multi-step method reduced the formation of unwanted LMO213 phases during synthesis compared to a one-pot method. NPD and XRPD analysis confirmed the layered structure of
Ec device thesis defence
The document summarizes research on fabricating electrochromic devices using transition metal oxides like MoO3 and WO3 as the active layer, and lower concentrations of HCl as the electrolyte. Thin films of MoO3 and WO3 were deposited using techniques like PLD and HWCVD. Characterization using XRD and Raman spectroscopy showed the films were phase pure. Electrochromic testing showed 10,000 shot MoO3 films cycled reversibly for 8 cycles, while WO3 films faded over multiple cycles. Lower HCl concentrations and hybrid MoO3/WO3 structures showed improved performance compared to higher concentrations and single component films.
NANOMATERIAL
This document summarizes the synthesis, characterization, and photocatalytic study of neodymium-doped cerium oxide nanoparticles. Cerium oxide and cerium oxide doped with neodymium in different ratios were synthesized via a sol-gel method and characterized using XRD, FT-IR, and TGA/DSC. XRD and FT-IR analysis confirmed the formation of cerium oxide with a cubic fluorite structure without phase changes after calcination. TGA/DSC showed the thermal stability of the samples. Photocatalytic testing found that doping with neodymium, especially at a ratio of 100:10, improved the photocatalytic activity for degrading methylene blue dye
Graphene coating
This document discusses using graphene as a coating to protect metals from oxidation. It begins with an overview of graphene and its properties, including being a single layer of carbon atoms with high strength, flexibility, electrical and thermal conductivity. The document then discusses two common methods for synthesizing graphene - chemical vapor deposition and mechanical exfoliation. An experiment is described where graphene is grown on copper and copper-nickel alloy substrates using CVD and characterized. Results show the graphene coating provides excellent oxidation resistance for the metals up to annealing temperatures of 500 degrees Celsius. In conclusion, graphene is an effective protective coating due to its chemical inertness, but the protection is lost after mechanical damage or higher temperature annealing.
Hybrid Graphene and Carbon Nanotube Thin Films
Presentation for my masters project on the synthesis and characterisation of hybrid graphene and carbon nanotube thin films.
PPT-PIEAS.pptx
The document discusses computational screening of 2D materials for different applications. It describes research being conducted at Allama Iqbal Open University on using computational methods to predict properties of 2D materials and study their potential applications in areas like photocatalysis, gas sensing, and thermoelectric devices. The research group is computationally investigating various 2D materials like MoSi2N4, WGe2N4, and WSi2N4 to understand their structural stability, electronic properties, and suitability for applications. The introduction provides background on 2D materials and their unique properties compared to bulk materials.
Rosa alejandra lukaszew tests of the gurenvich odel toward larger field gra...
SRF properties are inherently a surface phenomenon involving a material thickness of a few microns thus opening up the possibility of using thin film coatings to achieve a desired performance. I will describe our experimental attempts to test the superconducting/insulating/superconducting (SIS) multilayer model proposed by A. Gurevich [1] to shield the bulk of the cavity from vortex penetration and hence enable larger accelerating fields than presently possible.
Rosa alejandra lukaszew a review of the thin film techniques potentially ap...
This document discusses thin film techniques that could be applicable for superconducting radio frequency (SRF) cavities. It reviews various thin film deposition methods like sputtering, evaporation, and ion beam assisted deposition. Challenges in achieving high quality niobium films for SRF cavities are discussed, including issues like adhesion, purity, defects, grain size, stress. The document provides background on thin film nucleation and growth processes. It also summarizes some previous work done on niobium thin films at the College of William and Mary using DC magnetron sputtering and reactive sputtering.
Rosa alejandra lukaszew a review of the thin film techniques potentially ap...
SRF is a surface phenomenon where only ~10 penetration depths are needed (l=40 nm for niobium), thus it has been recognized for some time now that it would be economically convenient to use thin film coated cavities. But problems arise with defects within 1 or 2 l of the surface or on the surface, and insufficient attention has been paid to this topic, including trapping of impurities like oxygen in defects as well as surface roughness enabling magnetic field pinning sites. Earlier attempts at CERN applied standard sputter PVD methods, but the grain size for the CERN Nb/Cu films was 100 nm, which is 10,000 times smaller than for conventional SRF cavities with the ensuing problems that appear at grain boundaries. Thus, these prior attempts showed higher surface resistance and worst Q-slope than bulk. I will review more modern approaches using higher energetic PVD methods for thin film deposition which offer promise to achieve thin films with improved superconducting performance.
Linear effects in optical fibers
This narrated power point presentation attempts to analyse the reasons for attenuation in optical fibers due to linear effects such as absorption, scattering and fiber bend. The material will be useful for KTU final year B Tech students who prepare for the subject EC 405, Optical Communications.
BUIE21 Jan 15
This document summarizes research on using self-organization phenomena like dewetting and demixing to form nanocrystals. Dewetting of thin films can cause the formation of nanodroplets. Demixing in liquid crystals provides an ordered matrix for nanoparticle growth. Specifically, zinc stearate nanocrystals were formed by dewetting on cadmium and cobalt stearate templates. The nanocrystals had different structures depending on the template. Also, gold nano-prisms were formed in the liquid crystal MBBA using its functional groups to reduce gold salt and provide ordering during demixing. Characterization showed the highly crystalline nature of the nanoparticles.
Thermal barrier coatings (tbc)
Nanocoating GDZ is compared with Conventional YSZ coating for Hot Corrosion Resistance in presence of V2O5 and Na2SO4 salt which are formed at high temp in gas turbines.
21 Self assembly_1.pptx
Block copolymer self-assembly and anodized aluminum oxide templates are widely used for low-cost nanofabrication. Block copolymers can self-assemble into periodic patterns below 10nm in size but typically lack long-range order. Their assembly can be guided by techniques like electric fields, shear forces, and chemical patterning to improve ordering. The assembled structures can be used as etch masks or for electroplating to fabricate nanostructures. Anodized aluminum oxide forms hexagonal arrays of pores down to 20nm in size through a dissolution-oxidation process that can be controlled electrolytically. Both techniques enable the low-cost fabrication of periodic nanostructures and have been used to produce devices
Optical fiber laser
Optical fiber lasers operate based on stimulated emission of photons from excited atoms or molecules within an active medium, such as rare earth doped silica fibers. They were first developed in the 1960s and have several advantages over solid-state lasers including high beam quality, efficiency, and thermal management. Fiber lasers are fabricated by first making a preform via modified chemical vapor deposition to dope the silica with rare earth ions. The preform is then drawn into an optical fiber, which can be structured using fiber Bragg gratings to form the laser cavity. Applications include materials processing, telecommunications, medicine, and directed energy weapons.
IC Fabrication Process
Semiconductor device fabrication is the process used to create the integrated circuits that are present in everyday electrical and electronic devices. It is a multiple-step sequence of photo lithographic and chemical processing steps during which electronic circuits are gradually created on a wafer made of pure semiconducting material. Silicon is almost always used, but various compound semiconductors are used for specialized applications.
Microsystems Technologies: Basic concepts and terminology
This document discusses various microfabrication techniques for silicon and glass substrates, including photolithography, wet etching, and dry etching. Photolithography is used to transfer patterns to photoresist layers and involves steps like spinning, baking, masking, exposing, and developing the resist. Wet etching of silicon can be isotropic or anisotropic, with anisotropic techniques etching at different rates depending on crystal plane. Common anisotropic etchants include KOH, TMAH, and EDP. Dry etching uses plasma chemistries like SF6 and CF4 to isotropically etch silicon through the production of volatile SiFx species. Proper masking and doping can be used to control the etching profile and selectively etch silicon
Negative Photoresists in photolithography
A photoresist is a light-sensitive material used in several industrial processes, such as photolithography and photoengraving, to form a patterned coating on a surface.
thinfilms.pptx
CdxZn1-xS thin films were synthesized via chemical bath deposition for various cadmium compositions. XRD analysis showed the films were polycrystalline with hexagonal structure, and crystallite size varied with composition from 9.2 to 16.5 nm. Absorption spectra indicated the bandgap shifted from UV to visible with increasing cadmium content. Tauc plot analysis demonstrated the bandgap could be varied non-linearly from 2.4 to 3.7 eV by changing the cadmium composition, making CdxZn1-xS suitable for optoelectronic applications.
Similar to Band gap engineering of hybrid perovskites for solar cells (20)
Xiaoxing xi progress in the investigation of mg b2 thin films for srf cavit...
Xiaoxing xi progress in the investigation of mg b2 thin films for srf cavit...
Rosa alejandra lukaszew tests of the gurenvich odel toward larger field gra...
Rosa alejandra lukaszew tests of the gurenvich odel toward larger field gra...
Rosa alejandra lukaszew a review of the thin film techniques potentially ap...
Rosa alejandra lukaszew a review of the thin film techniques potentially ap...
Rosa alejandra lukaszew a review of the thin film techniques potentially ap...
Rosa alejandra lukaszew a review of the thin film techniques potentially ap...
Microsystems Technologies: Basic concepts and terminology
Microsystems Technologies: Basic concepts and terminology
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Bob Reedy - Nitrate in Texas Groundwater.pdf
Presented at June 6-7 Texas Alliance of Groundwater Districts Business Meeting
Applied Science: Thermodynamics, Laws & Methodology.pdf
When I was asked to give a companion lecture in support of ‘The Philosophy of Science’ (https://shorturl.at/4pUXz) I decided not to walk through the detail of the many methodologies in order of use. Instead, I chose to employ a long standing, and ongoing, scientific development as an exemplar. And so, I chose the ever evolving story of Thermodynamics as a scientific investigation at its best.
Conducted over a period of >200 years, Thermodynamics R&D, and application, benefitted from the highest levels of professionalism, collaboration, and technical thoroughness. New layers of application, methodology, and practice were made possible by the progressive advance of technology. In turn, this has seen measurement and modelling accuracy continually improved at a micro and macro level.
Perhaps most importantly, Thermodynamics rapidly became a primary tool in the advance of applied science/engineering/technology, spanning micro-tech, to aerospace and cosmology. I can think of no better a story to illustrate the breadth of scientific methodologies and applications at their best.
8.Isolation of pure cultures and preservation of cultures.pdf
Isolation of pure culture, its various method.
waterlessdyeingtechnolgyusing carbon dioxide chemicalspdf
The technology uses reclaimed CO₂ as the dyeing medium in a closed loop process. When pressurized, CO₂ becomes supercritical (SC-CO₂). In this state CO₂ has a very high solvent power, allowing the dye to dissolve easily.
The debris of the ‘last major merger’ is dynamically young
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
原版制作(carleton毕业证书)卡尔顿大学毕业证硕士文凭原版一模一样
原版纸张【微信：741003700 】【(carleton毕业证书)卡尔顿大学毕业证】【微信：741003700 】学位证，留信认证（真实可查，永久存档）offer、雅思、外壳等材料/诚信可靠,可直接看成品样本，帮您解决无法毕业带来的各种难题！外壳，原版制作，诚信可靠，可直接看成品样本。行业标杆！精益求精，诚心合作，真诚制作！多年品质 ,按需精细制作，24小时接单,全套进口原装设备。十五年致力于帮助留学生解决难题，包您满意。
本公司拥有海外各大学样板无数，能完美还原海外各大学 Bachelor Diploma degree, Master Degree Diploma
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留信网认证的作用:
1:该专业认证可证明留学生真实身份
2:同时对留学生所学专业登记给予评定
3:国家专业人才认证中心颁发入库证书
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The use of Nauplii and metanauplii artemia in aquaculture (brine shrimp).pptx
Although Artemia has been known to man for centuries, its use as a food for the culture of larval organisms apparently began only in the 1930s, when several investigators found that it made an excellent food for newly hatched fish larvae (Litvinenko et al., 2023). As aquaculture developed in the 1960s and ‘70s, the use of Artemia also became more widespread, due both to its convenience and to its nutritional value for larval organisms (Arenas-Pardo et al., 2024). The fact that Artemia dormant cysts can be stored for long periods in cans, and then used as an off-the-shelf food requiring only 24 h of incubation makes them the most convenient, least labor-intensive, live food available for aquaculture (Sorgeloos & Roubach, 2021). The nutritional value of Artemia, especially for marine organisms, is not constant, but varies both geographically and temporally. During the last decade, however, both the causes of Artemia nutritional variability and methods to improve poorquality Artemia have been identified (Loufi et al., 2024).
Brine shrimp (Artemia spp.) are used in marine aquaculture worldwide. Annually, more than 2,000 metric tons of dry cysts are used for cultivation of fish, crustacean, and shellfish larva. Brine shrimp are important to aquaculture because newly hatched brine shrimp nauplii (larvae) provide a food source for many fish fry (Mozanzadeh et al., 2021). Culture and harvesting of brine shrimp eggs represents another aspect of the aquaculture industry. Nauplii and metanauplii of Artemia, commonly known as brine shrimp, play a crucial role in aquaculture due to their nutritional value and suitability as live feed for many aquatic species, particularly in larval stages (Sorgeloos & Roubach, 2021).
Phenomics assisted breeding in crop improvement
As the population is increasing and will reach about 9 billion upto 2050. Also due to climate change, it is difficult to meet the food requirement of such a large population. Facing the challenges presented by resource shortages, climate
change, and increasing global population, crop yield and quality need to be improved in a sustainable way over the coming decades. Genetic improvement by breeding is the best way to increase crop productivity. With the rapid progression of functional
genomics, an increasing number of crop genomes have been sequenced and dozens of genes influencing key agronomic traits have been identified. However, current genome sequence information has not been adequately exploited for understanding
the complex characteristics of multiple gene, owing to a lack of crop phenotypic data. Efficient, automatic, and accurate technologies and platforms that can capture phenotypic data that can
be linked to genomics information for crop improvement at all growth stages have become as important as genotyping. Thus,
high-throughput phenotyping has become the major bottleneck restricting crop breeding. Plant phenomics has been defined as the high-throughput, accurate acquisition and analysis of multi-dimensional phenotypes
during crop growing stages at the organism level, including the cell, tissue, organ, individual plant, plot, and field levels. With the rapid development of novel sensors, imaging technology,
and analysis methods, numerous infrastructure platforms have been developed for phenotyping.
在线办理(salfor毕业证书)索尔福德大学毕业证毕业完成信一模一样
学校原件一模一样【微信：741003700 】《(salfor毕业证书)索尔福德大学毕业证》【微信：741003700 】学位证，留信认证（真实可查，永久存档）原件一模一样纸张工艺/offer、雅思、外壳等材料/诚信可靠,可直接看成品样本，帮您解决无法毕业带来的各种难题！外壳，原版制作，诚信可靠，可直接看成品样本。行业标杆！精益求精，诚心合作，真诚制作！多年品质 ,按需精细制作，24小时接单,全套进口原装设备。十五年致力于帮助留学生解决难题，包您满意。
本公司拥有海外各大学样板无数，能完美还原。
1:1完美还原海外各大学毕业材料上的工艺：水印，阴影底纹，钢印LOGO烫金烫银，LOGO烫金烫银复合重叠。文字图案浮雕、激光镭射、紫外荧光、温感、复印防伪等防伪工艺。材料咨询办理、认证咨询办理请加学历顾问Q/微741003700
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留信网认证的作用:
1:该专业认证可证明留学生真实身份
2:同时对留学生所学专业登记给予评定
3:国家专业人才认证中心颁发入库证书
4:这个认证书并且可以归档倒地方
5:凡事获得留信网入网的信息将会逐步更新到个人身份内，将在公安局网内查询个人身份证信息后，同步读取人才网入库信息
6:个人职称评审加20分
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20240520 Planning a Circuit Simulator in JavaScript.pptx
Evaporation step counter work. I have done a physical experiment.
(Work in progress.)
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
Deep Software Variability and Frictionless Reproducibility
Deep Software Variability and Frictionless ReproducibilityUniversity of Rennes, INSA Rennes, Inria/IRISA, CNRS
The ability to recreate computational results with minimal effort and actionable metrics provides a solid foundation for scientific research and software development. When people can replicate an analysis at the touch of a button using open-source software, open data, and methods to assess and compare proposals, it significantly eases verification of results, engagement with a diverse range of contributors, and progress. However, we have yet to fully achieve this; there are still many sociotechnical frictions.
Inspired by David Donoho's vision, this talk aims to revisit the three crucial pillars of frictionless reproducibility (data sharing, code sharing, and competitive challenges) with the perspective of deep software variability.
Our observation is that multiple layers — hardware, operating systems, third-party libraries, software versions, input data, compile-time options, and parameters — are subject to variability that exacerbates frictions but is also essential for achieving robust, generalizable results and fostering innovation. I will first review the literature, providing evidence of how the complex variability interactions across these layers affect qualitative and quantitative software properties, thereby complicating the reproduction and replication of scientific studies in various fields.
I will then present some software engineering and AI techniques that can support the strategic exploration of variability spaces. These include the use of abstractions and models (e.g., feature models), sampling strategies (e.g., uniform, random), cost-effective measurements (e.g., incremental build of software configurations), and dimensionality reduction methods (e.g., transfer learning, feature selection, software debloating).
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Band gap engineering of hybrid perovskites for solar cells
- 1. Band gap engineering of hybrid organic inorganic lead-halide perovskites Kirill Popov David Cahen Group Department of Materials and Interfaces
- 2. What is a band?
- 3. Band structure of solids
- 4. Key band positioning types
- 5. Key band positioning types
- 6. The principle of photovoltaics
- 7. Solar radiation Maximum in spectrum ∽ semiconductors band gap
- 8. Energy loss pathways • Radiative recombination • Relaxation to band edges • Blackbody radiation • Solar spectrum is not uniform • Other: non-radiative recombination, finite mobility
- 9. Energy loss pathways • Radiative recombination • Relaxation to band edges • Blackbody radiation • Solar spectrum is not uniform • Other: non-radiative recombination, finite mobility
- 10. Energy loss pathways • Radiative recombination • Relaxation to band edges • Blackbody radiation • Solar spectrum is not uniform • Other: non-radiative recombination, finite mobility
- 12. Shockley-Queisser Limit 33.7% for Egap of 1.34 eV
- 13. How to overcome the limit?
- 14. How to overcome the limit? Multijunction solar cells: «stacking»
- 15. Perovskite CaTiO3 Lev Perovski (1792–1856) • Fairly popular structural type among ABX3 compounds • May undergo distortions: axial stretch, octahedra twist,..
- 16. Hybrid lead halide perovskites •Several easy preparation techniques exist •Cheap precursors, no rare elements •Relatively good conductance
- 17. MAPbX3 Band gap can be tuned by varying halide composition
- 19. Device efficiency x Recent reports of 19.3% efficiency!
- 20. Device architecture Au HTM Absorber ETM FTO Glass HTM - hole transport material ETM - electron transport material FTO - fluorine-doped tin oxide (transparent conductor)
- 21. Spin-coating
- 22. Two-step deposition: the procedure 1. Spin-coating PbBr2 and PbI2 2. Dipping the films in MABrxI1-x solutions
- 23. The project • Fabrication of MAPb(I,Br)3 films by two-step deposition • Characterization of the films compositions and band gaps by their optical properties • Optimization of the fabrication procedure
- 24. First step • Samples pre-heated to 100 ºC • 1 mol/l solutions of PbX2 in DMF at 100 ºC used • Spin-coating parameters: 6500 rpm, 550 rpm/sec acceleration, 90 sec • Annealing after spin-coating: 70 ºC, 30 min • Profilometry: 700-800 nm thickness
- 25. Second step • Solution of MABr and MAI in iPrOH • C (total) = C (MA+) = 0.05 mol/l • 1h dipping time
- 26. Deposition on glass • Adhesion between glass and perovskite is quite low • Fast rate of film degradation on exposure to air is observed 0 10 20 30 40 50 60 70 80 90 100 PbBr2 %Br in solution
- 27. Deposition on mesoporous Al2O3 • Mp-alumina deposited by spin-coating colloidal Al2O3 and ethylcellulose solution with post-annealing at 550ºC for 2 hours • Significantly improved mechanical stability of the films PbBr2 0 20 40 60 80 100 %Br in solution 0 20 40 60 80 100 %Br in solution PbI2
- 28. Light absorbance Absorption edge corresponds to band gap value
- 29. Photoluminescence via PbBr2 via PbI2
- 30. Band gap values • JH Noh et al.: Eg = 1.57 + 0.39x + 0.33x2 (eV) for MAPb(I1-xBrx)3 • Eg = 1.54 + 0.16x + 0.45x2 (eV) for films prepared by dipping PbI2 in MAI1-xBrx solution
- 31. Adding post-annealing step • Samples have been annealed at 100 ºC for 20 min • Visible degradation signs disappear at the cost of impaired uniformity PbBr2 0 20 40 60 80 100 %Br in solution 0 20 40 60 80 100 %Br in solution PbI2
- 32. Band gaps • Eg = 0.41x+1.53 (eV) for perovskites prepared by dipping PbI2 in MAI1-xBrx solution
- 33. Conclusions • Methyl ammonium lead iodide bromide band gap may be engineered between 1.55 and 2.29 eV by changing solution composition in two-step deposition process • Perovskite films are significantly less likely to be damaged mechanically if mesoporous scaffold is used • Tetragonal MAPbI3 phase formation is found to be preferable at all anion compositions of dipping solution • Annealing perovskites after dipping prevents instant degradation but affects uniform film formation process • Annealing converts quadratic dependence of band gap value on solution composition to linear
- 34. Future directions • Elemental and phase characterization of the films • Investigation into film degradation and its effect perovskite electronic structure • Unfixing different parameters - total concentration, time, annealing temperature etc.
- 35. Thanks Igal Levine Professor David Cahen and his group Professor Gary Hodes and his group Kupcinet-Getz Summer Program