This document summarizes research into replacing lead with barium in hybrid perovskite materials for optoelectronics. The researcher aimed to synthesize and characterize methylammonium barium iodide (CH3NH3BaI3) as a potential non-toxic alternative to the commonly used methylammonium lead triiodide. Solution processing was used to combine barium iodide and methylammonium iodide, but characterization techniques like UV-Vis spectroscopy, photoluminescence, and XRD did not show evidence that the intended perovskite material was formed. The film also proved unstable when exposed to air. Further experimentation is needed to determine better synthesis and processing methods.
This study investigates copper iodide (CuI) as an inorganic hole conductor for organolead halide perovskite solar cells. The researchers fabricated solar cells using CuI deposited via an automated drop casting technique. Compared to the conventional organic hole conductor spiro-OMeTAD, the CuI-based devices showed higher photocurrent stability and fill factor but lower open-circuit voltage. Impedance spectroscopy indicated the lower voltage was due to higher recombination rates in the CuI devices. However, CuI exhibited nearly two orders of magnitude higher hole conductivity than spiro-OMeTAD, suggesting its potential as a lower-cost replacement for organic hole transport materials.
Perovskites-based Solar Cells: The challenge of material choice for p-i-n per...Akinola Oyedele
Perovskite-based PV have triggered widespread interest in the scientific community because these materials offer the attractive combinations of low cost and theoretically high efficiency. However, several challenges must be overcome for these relatively new PV materials. Among the many important challenges, one is the choice of materials to be used in thin film PV devices..
Based on fundamental principles of solar photovoltaics, this problem focuses on two aspects of the perovskite system:
1) Based on a planar p-i-n device structure, a potential list of p- and n-type charge collecting layers as well as the conductive contacts that could be used with a promising perovskite absorber material was identified, and a proper justification for the selection of each material in the device was given.
2) Three theoretical p-i-n type solar cells were made with the chosen materials and appropriate conductive contacts.
The document discusses perovskite solar cells. It begins by defining perovskites and their crystal structure. It then discusses several important studies on perovskite solar cells that improved their efficiency over time, including studies published in 2012, 2013, 2014 and 2015 that achieved efficiencies up to 19.3%. It also reviews factors that affect the performance and stability of perovskite solar cells, such as humidity, UV light, annealing temperature, and the choice of electron transport material. In conclusion, it summarizes that perovskite solar cells have advantages over traditional silicon solar cells like easier processing, higher efficiency potential, flexibility and lower cost.
Perovskite solar cells the birth of new era in photovoltaics.Krishna Patel
This document discusses perovskite solar cells. It begins by defining perovskite and its crystal structure, then discusses the properties and fabrication methods of perovskite solar cells. Some key advantages of perovskite solar cells are their low cost fabrication using solution processing and high absorption coefficient. However, challenges remain around toxicity, stability, and replacing lead. The document also briefly summarizes some large solar parks in India and the country's growing solar capacity.
Organometal halide perovskite solar cells: Degradation and stabilityTaame Abraha Berhe
Organometal halide perovskite solar cells have evolved in an exponential manner in the two key areas of
efficiency and stability. The power conversion efficiency (PCE) reached 20.1% late last year. The key disquiet
was stability, which has been limiting practical application, but now the state of the art is promising, being
measured in thousands of hours. These improvements have been achieved through the application of
different materials, interfaces and device architecture optimizations, especially after the investigation of hole
conductor free mesoporous devices incorporating carbon electrodes, which promise stable, low cost
and easy device fabrication methods. However, this work is still far from complete.
This presentation summarizes history and recent development of perovskite solar cells. If you have any questions or comments, you can reach me at agassifeng@gmail.com
Use of conventional sources of energy to generate electricity is
increasing rapidly due to growing energy demands. This is a
major cause of pollution as well and also is an environmental
concern for future. Considering this, there is lot of R&D going on in the field of alternate energy sources with recent advancements in technology. One of the most recent advancement is the perovskite solar technology in the photovoltaics industry. The power conversion efficiency of perovskite solar cells has been improved from 9.7 to 20.1% within 4 years which is the fastest advancement ever in the photovoltaic industry. Such a high photovoltaic performance can be attributed to optically high absorption characteristics of the hybrid lead perovskite materials. In this review, different perovskite materials are breifly discussed along with the fundamental details of the hybrid lead halide perovskite materials. The fabrication techniques, stability, device structure and the chemistry of the perovskite structure are also briefly described aiming for a better understanding of these materials and thus highly efficient perovskite solar cell devices. The main focus of this resarch is to understand possible methods to reduce toxicity due to lead and to improve Perovskite stability.
Perovskite Crystals: A Bright Future in Solar TechnologyReid Barton
1) The student created perovskite crystal solar cells using different precursor solutions and measured their voltage outputs. Cells using a 2:1 ratio of formamidinium chloride to lead iodide performed best, achieving up to 520 mV.
2) A tandem cell combining perovskite and silicon layers performed better than either individually, demonstrating potential for improved efficiencies.
3) The higher chloride concentration in the optimal precursor solution likely increased the crystal's band gap, resulting in a higher output voltage. While rudimentary, the experiments provided insight into effective precursor compositions.
This study investigates copper iodide (CuI) as an inorganic hole conductor for organolead halide perovskite solar cells. The researchers fabricated solar cells using CuI deposited via an automated drop casting technique. Compared to the conventional organic hole conductor spiro-OMeTAD, the CuI-based devices showed higher photocurrent stability and fill factor but lower open-circuit voltage. Impedance spectroscopy indicated the lower voltage was due to higher recombination rates in the CuI devices. However, CuI exhibited nearly two orders of magnitude higher hole conductivity than spiro-OMeTAD, suggesting its potential as a lower-cost replacement for organic hole transport materials.
Perovskites-based Solar Cells: The challenge of material choice for p-i-n per...Akinola Oyedele
Perovskite-based PV have triggered widespread interest in the scientific community because these materials offer the attractive combinations of low cost and theoretically high efficiency. However, several challenges must be overcome for these relatively new PV materials. Among the many important challenges, one is the choice of materials to be used in thin film PV devices..
Based on fundamental principles of solar photovoltaics, this problem focuses on two aspects of the perovskite system:
1) Based on a planar p-i-n device structure, a potential list of p- and n-type charge collecting layers as well as the conductive contacts that could be used with a promising perovskite absorber material was identified, and a proper justification for the selection of each material in the device was given.
2) Three theoretical p-i-n type solar cells were made with the chosen materials and appropriate conductive contacts.
The document discusses perovskite solar cells. It begins by defining perovskites and their crystal structure. It then discusses several important studies on perovskite solar cells that improved their efficiency over time, including studies published in 2012, 2013, 2014 and 2015 that achieved efficiencies up to 19.3%. It also reviews factors that affect the performance and stability of perovskite solar cells, such as humidity, UV light, annealing temperature, and the choice of electron transport material. In conclusion, it summarizes that perovskite solar cells have advantages over traditional silicon solar cells like easier processing, higher efficiency potential, flexibility and lower cost.
Perovskite solar cells the birth of new era in photovoltaics.Krishna Patel
This document discusses perovskite solar cells. It begins by defining perovskite and its crystal structure, then discusses the properties and fabrication methods of perovskite solar cells. Some key advantages of perovskite solar cells are their low cost fabrication using solution processing and high absorption coefficient. However, challenges remain around toxicity, stability, and replacing lead. The document also briefly summarizes some large solar parks in India and the country's growing solar capacity.
Organometal halide perovskite solar cells: Degradation and stabilityTaame Abraha Berhe
Organometal halide perovskite solar cells have evolved in an exponential manner in the two key areas of
efficiency and stability. The power conversion efficiency (PCE) reached 20.1% late last year. The key disquiet
was stability, which has been limiting practical application, but now the state of the art is promising, being
measured in thousands of hours. These improvements have been achieved through the application of
different materials, interfaces and device architecture optimizations, especially after the investigation of hole
conductor free mesoporous devices incorporating carbon electrodes, which promise stable, low cost
and easy device fabrication methods. However, this work is still far from complete.
This presentation summarizes history and recent development of perovskite solar cells. If you have any questions or comments, you can reach me at agassifeng@gmail.com
Use of conventional sources of energy to generate electricity is
increasing rapidly due to growing energy demands. This is a
major cause of pollution as well and also is an environmental
concern for future. Considering this, there is lot of R&D going on in the field of alternate energy sources with recent advancements in technology. One of the most recent advancement is the perovskite solar technology in the photovoltaics industry. The power conversion efficiency of perovskite solar cells has been improved from 9.7 to 20.1% within 4 years which is the fastest advancement ever in the photovoltaic industry. Such a high photovoltaic performance can be attributed to optically high absorption characteristics of the hybrid lead perovskite materials. In this review, different perovskite materials are breifly discussed along with the fundamental details of the hybrid lead halide perovskite materials. The fabrication techniques, stability, device structure and the chemistry of the perovskite structure are also briefly described aiming for a better understanding of these materials and thus highly efficient perovskite solar cell devices. The main focus of this resarch is to understand possible methods to reduce toxicity due to lead and to improve Perovskite stability.
Perovskite Crystals: A Bright Future in Solar TechnologyReid Barton
1) The student created perovskite crystal solar cells using different precursor solutions and measured their voltage outputs. Cells using a 2:1 ratio of formamidinium chloride to lead iodide performed best, achieving up to 520 mV.
2) A tandem cell combining perovskite and silicon layers performed better than either individually, demonstrating potential for improved efficiencies.
3) The higher chloride concentration in the optimal precursor solution likely increased the crystal's band gap, resulting in a higher output voltage. While rudimentary, the experiments provided insight into effective precursor compositions.
This document discusses perovskite solar cells as a promising new material for next generation solar cells. It provides an overview of solar cell basics and the emergence of perovskites. Key features of perovskites discussed include their crystal structure, high optical absorption coefficient, excellent charge carrier transport properties, and tunable bandgap. Methods for preparing perovskite solar cells are described, along with future challenges such as improving stability and replacing toxic lead.
Perovskite Solar Cells
a short general overview presentation
hadi maghsoudi
device structure
crystal structure
preparation synthesis method
review papers
Perovskite solar cells - An Introduction, By Dawn John MullasseryDawn John Mullassery
Perovskite solar cells (PSCs) are a promising photovoltaic technology that has seen rapid increases in power conversion efficiency from 9.7% to over 20% in just a few years. PSCs offer advantages over other solar cell technologies in terms of cost of raw materials, fabrication, and efficiency. However, research is still needed to address challenges such as stability in the presence of moisture and the toxicity of lead used in early PSC designs. Future work aims to remove toxicity concerns and develop thin film and flexible PSC designs to enable widespread commercialization of this emerging solar technology.
The document discusses improving light trapping in perovskite solar cells by developing a nano-structured transparent contact. The goal is to enhance the quantum efficiency, short-circuit current, and open-circuit voltage of perovskite solar cells to increase overall efficiency. A methodology is proposed that involves simulating flat and nano-cone structured perovskite solar cells and modifying the nano-cone structure parameters to optimize light trapping. Simulation results show reduced power losses and reflections with the nano-cone structures compared to flat structures, demonstrating enhanced light trapping. Future work could involve developing lead-free perovskites and texturing multiple layers.
Progress in all inorganic perovskite solar cellMd Ataul Mamun
Since their first introduction in the research arena, the hybrid organic-inorganic perovskite photovoltaic cells have been showing frequent record breaking power conversion efficiencies (PCEs). Despite the rapid increase in PCE by engaging new perovskite materials as active layers as well as new fabrication techniques, their stability remains too poor to go for a mass production. Mainly the organic materials in the hybrid PSCs are responsible for this instability. Consequently, very recently, different approaches are taken to replace these organic components by inorganic ones to fabricate all-inorganic PSCs. Though these first-generation all-inorganic PSCs are yet to produce competitive PCEs like their counterparts, they have already demonstrated superb stability to be a propitious bidder for solar cell energy yielding. The state-of-the-art quantum dots based cells shown efficiency as high as 10.77% and intact stability for months.
Research proposal on organic-inorganic halide perovskite light harvesting mat...Rajan K. Singh
Organic-Inorganic perovskite materials has many applications in the field of opto-electronics such as photo-voltaic cells, LEDs, sensors, memory devices etc. due to its excellent optical and electrical properties. Presence of Pb in such type of perovskite is the biggest challenge for researchers.
The document discusses various technologies for developing solar cells with efficiencies beyond the Shockley-Queisser limit of 30%. Multi-junction cells use multiple solar cells to selectively absorb different wavelengths of light. Intermediate-band cells use a partially filled energy band to increase current while maintaining voltage. Hot-carrier cells convert excess photon energy above the bandgap into electrical energy. These methods aim to optimize solar absorption and energy conversion.
Advantages and problems of perovskite solar cellalfachemistry
This article mainly introduces the advantages and problems of perovskite solar cell. Visit https://www.alfa-chemistry.com/products/perovskite-solar-cells-139.htm for more information.
This study aimed to replace lead in perovskite materials with barium to make optoelectronic devices more environmentally sustainable. The researchers synthesized barium iodide and attempted to intercalate methylammonium iodide to form methylammonium barium triiodide perovskite as described in a manuscript by Kumar et al. Characterization of spin-coated films found no evidence of perovskite formation and the solutions degraded when exposed to air, inconsistent with Kumar's results. Further work is needed to explore alternative precursors, synthesis methods, and characterization of any photonic properties.
A perovskite solar cell is a type of solar cell which includes a perovskite structured compound, most commonly a hybrid organic-inorganic lead or tin halide-based material, as the light-harvesting active layer.
This document summarizes research on improving the stability of perovskite solar cells. It discusses using tin instead of lead in perovskite materials to reduce toxicity. A carbon and epoxy electrode is also proposed to improve moisture stability. Test results show the carbon-epoxy electrode maintains solar cell efficiency for over 20 days in humid conditions, while a carbon-only device degrades after 16 days. Coating the carbon-epoxy with silver further enhances moisture resistance and electrical conductivity.
R.P.H. Chang presented research on using nanotechnology to develop future solar cells, supercapacitors, and sensors. Three examples from his lab were discussed: (1) hybrid solar cells using materials like SnIx-based perovskites as sensitizers, (2) integrating supercapacitors for energy storage, and (3) plasmonic sensors in the infrared region. Nanotechnology is urgently needed to address global problems through worldwide collaboration and education on technologies like more efficient solar cells and energy storage solutions.
Perovskite: introduction, classification, structure of perovskite, method to synthesis, characterization by XRD and UV- vis spectroscopy , lambert beer's law, material properties and advantage and application.
This document summarizes a student group's progress defense presentation on their research developing nano-structured transparent contacts for dye sensitized solar cells. The group reports on their goals of analyzing photon absorption characteristics and enhancing efficiency. Their experimental design involves modeling amorphous silicon layers in a solar cell. Simulation results so far are presented. The group's timeline shows further analysis planned through the end of the year, culminating in a final defense. References cited research on TiO2 anodes, organic sensitizers, and carbon nanotube photoanodes to enhance dye sensitized solar cell efficiency.
An introduction of perovskite solar cellsalfachemistry
This article introduces the development, structure and work mechanism of perovskite solar cells. Visit https://www.alfa-chemistry.com/products/perovskite-solar-cells-139.htm for more information.
Device simulation of perovskite solar cells with molybdenum disulfide as acti...journalBEEI
Organo-halide Perovskite Solar Cells (PSC) have been reported to achieve remarkably high power conversion efficiency (PCE). A thorough understanding of the role of each component in solar cells and their effect as a whole is still required for further improvement in PCE. In this paper, the effect of Molybdenum Disulfide (MoS2) in PSC with mesoporous structure configuration was analyzed using Solar Cell Capacitance Simulator (SCAPS). With the MoS2 layer which having two-fold function, acting as a protective layer, by preventing the formation of shunt contacts between perovskite and Au electrode, and as a hole transport material (HTM) from the perovskite to the Spiro-OMETAD. As simulated, PSC demonstrates a PCE, ŋ of 13.1%, along with stability compared to typical structure of PSC without MoS2 (Δ ŋ/ŋ=-9% vs. Δ ŋ/ŋ=-6%). The results pave the way towards the implementation of MoS2 as a material able to boost shelf life which very useful for new material choice and optimization of HTMs
1) The construction of tunnels for the Kallang/Paya Lebar Expressway (KPE) project faced many challenges due to the area's geology and existing infrastructure, with one of the greatest challenges being the construction of tunnels under the Pelton Canal.
2) A half-box tunnel construction method was used to build the tunnels under the Pelton Canal, which involved diverting the canal, installing retaining walls and piles, and excavating each half of the tunnel in stages while ensuring the stability of the temporary diversion structures.
3) The tunnel construction between PIE and Ubi Road 2 is now over 85% complete, with various sections of tunnel and infrastructure works at different stages of progress, and rein
This document discusses perovskite solar cells as a promising new material for next generation solar cells. It provides an overview of solar cell basics and the emergence of perovskites. Key features of perovskites discussed include their crystal structure, high optical absorption coefficient, excellent charge carrier transport properties, and tunable bandgap. Methods for preparing perovskite solar cells are described, along with future challenges such as improving stability and replacing toxic lead.
Perovskite Solar Cells
a short general overview presentation
hadi maghsoudi
device structure
crystal structure
preparation synthesis method
review papers
Perovskite solar cells - An Introduction, By Dawn John MullasseryDawn John Mullassery
Perovskite solar cells (PSCs) are a promising photovoltaic technology that has seen rapid increases in power conversion efficiency from 9.7% to over 20% in just a few years. PSCs offer advantages over other solar cell technologies in terms of cost of raw materials, fabrication, and efficiency. However, research is still needed to address challenges such as stability in the presence of moisture and the toxicity of lead used in early PSC designs. Future work aims to remove toxicity concerns and develop thin film and flexible PSC designs to enable widespread commercialization of this emerging solar technology.
The document discusses improving light trapping in perovskite solar cells by developing a nano-structured transparent contact. The goal is to enhance the quantum efficiency, short-circuit current, and open-circuit voltage of perovskite solar cells to increase overall efficiency. A methodology is proposed that involves simulating flat and nano-cone structured perovskite solar cells and modifying the nano-cone structure parameters to optimize light trapping. Simulation results show reduced power losses and reflections with the nano-cone structures compared to flat structures, demonstrating enhanced light trapping. Future work could involve developing lead-free perovskites and texturing multiple layers.
Progress in all inorganic perovskite solar cellMd Ataul Mamun
Since their first introduction in the research arena, the hybrid organic-inorganic perovskite photovoltaic cells have been showing frequent record breaking power conversion efficiencies (PCEs). Despite the rapid increase in PCE by engaging new perovskite materials as active layers as well as new fabrication techniques, their stability remains too poor to go for a mass production. Mainly the organic materials in the hybrid PSCs are responsible for this instability. Consequently, very recently, different approaches are taken to replace these organic components by inorganic ones to fabricate all-inorganic PSCs. Though these first-generation all-inorganic PSCs are yet to produce competitive PCEs like their counterparts, they have already demonstrated superb stability to be a propitious bidder for solar cell energy yielding. The state-of-the-art quantum dots based cells shown efficiency as high as 10.77% and intact stability for months.
Research proposal on organic-inorganic halide perovskite light harvesting mat...Rajan K. Singh
Organic-Inorganic perovskite materials has many applications in the field of opto-electronics such as photo-voltaic cells, LEDs, sensors, memory devices etc. due to its excellent optical and electrical properties. Presence of Pb in such type of perovskite is the biggest challenge for researchers.
The document discusses various technologies for developing solar cells with efficiencies beyond the Shockley-Queisser limit of 30%. Multi-junction cells use multiple solar cells to selectively absorb different wavelengths of light. Intermediate-band cells use a partially filled energy band to increase current while maintaining voltage. Hot-carrier cells convert excess photon energy above the bandgap into electrical energy. These methods aim to optimize solar absorption and energy conversion.
Advantages and problems of perovskite solar cellalfachemistry
This article mainly introduces the advantages and problems of perovskite solar cell. Visit https://www.alfa-chemistry.com/products/perovskite-solar-cells-139.htm for more information.
This study aimed to replace lead in perovskite materials with barium to make optoelectronic devices more environmentally sustainable. The researchers synthesized barium iodide and attempted to intercalate methylammonium iodide to form methylammonium barium triiodide perovskite as described in a manuscript by Kumar et al. Characterization of spin-coated films found no evidence of perovskite formation and the solutions degraded when exposed to air, inconsistent with Kumar's results. Further work is needed to explore alternative precursors, synthesis methods, and characterization of any photonic properties.
A perovskite solar cell is a type of solar cell which includes a perovskite structured compound, most commonly a hybrid organic-inorganic lead or tin halide-based material, as the light-harvesting active layer.
This document summarizes research on improving the stability of perovskite solar cells. It discusses using tin instead of lead in perovskite materials to reduce toxicity. A carbon and epoxy electrode is also proposed to improve moisture stability. Test results show the carbon-epoxy electrode maintains solar cell efficiency for over 20 days in humid conditions, while a carbon-only device degrades after 16 days. Coating the carbon-epoxy with silver further enhances moisture resistance and electrical conductivity.
R.P.H. Chang presented research on using nanotechnology to develop future solar cells, supercapacitors, and sensors. Three examples from his lab were discussed: (1) hybrid solar cells using materials like SnIx-based perovskites as sensitizers, (2) integrating supercapacitors for energy storage, and (3) plasmonic sensors in the infrared region. Nanotechnology is urgently needed to address global problems through worldwide collaboration and education on technologies like more efficient solar cells and energy storage solutions.
Perovskite: introduction, classification, structure of perovskite, method to synthesis, characterization by XRD and UV- vis spectroscopy , lambert beer's law, material properties and advantage and application.
This document summarizes a student group's progress defense presentation on their research developing nano-structured transparent contacts for dye sensitized solar cells. The group reports on their goals of analyzing photon absorption characteristics and enhancing efficiency. Their experimental design involves modeling amorphous silicon layers in a solar cell. Simulation results so far are presented. The group's timeline shows further analysis planned through the end of the year, culminating in a final defense. References cited research on TiO2 anodes, organic sensitizers, and carbon nanotube photoanodes to enhance dye sensitized solar cell efficiency.
An introduction of perovskite solar cellsalfachemistry
This article introduces the development, structure and work mechanism of perovskite solar cells. Visit https://www.alfa-chemistry.com/products/perovskite-solar-cells-139.htm for more information.
Device simulation of perovskite solar cells with molybdenum disulfide as acti...journalBEEI
Organo-halide Perovskite Solar Cells (PSC) have been reported to achieve remarkably high power conversion efficiency (PCE). A thorough understanding of the role of each component in solar cells and their effect as a whole is still required for further improvement in PCE. In this paper, the effect of Molybdenum Disulfide (MoS2) in PSC with mesoporous structure configuration was analyzed using Solar Cell Capacitance Simulator (SCAPS). With the MoS2 layer which having two-fold function, acting as a protective layer, by preventing the formation of shunt contacts between perovskite and Au electrode, and as a hole transport material (HTM) from the perovskite to the Spiro-OMETAD. As simulated, PSC demonstrates a PCE, ŋ of 13.1%, along with stability compared to typical structure of PSC without MoS2 (Δ ŋ/ŋ=-9% vs. Δ ŋ/ŋ=-6%). The results pave the way towards the implementation of MoS2 as a material able to boost shelf life which very useful for new material choice and optimization of HTMs
1) The construction of tunnels for the Kallang/Paya Lebar Expressway (KPE) project faced many challenges due to the area's geology and existing infrastructure, with one of the greatest challenges being the construction of tunnels under the Pelton Canal.
2) A half-box tunnel construction method was used to build the tunnels under the Pelton Canal, which involved diverting the canal, installing retaining walls and piles, and excavating each half of the tunnel in stages while ensuring the stability of the temporary diversion structures.
3) The tunnel construction between PIE and Ubi Road 2 is now over 85% complete, with various sections of tunnel and infrastructure works at different stages of progress, and rein
Manual do Pré-Amplificador FOCUSRITE Octopre MKIIHabro Group
Pré-amplificador de microfones Focusrite OctoPre MkII, 8 canais de entrada combo XLR Mic/Line/Instrument, 2 saídas ópticas digitais ADAT, 8 canais por porta (16 no total) em 44.1 e 48 kHz, 8 saídas Line 1/4"-P10, Phantom power.
El documento presenta la lista de canciones que se tocaron en el programa de radio El Mañanero el 15 de abril, incluyendo "All Right, Okay, You Win" de Joe Williams de su álbum de 2001, "Ring of Fire" interpretada por Joaquin Phoenix en la banda sonora de la película Walk the Line de 2005, y "Fina Estampa" de Caetano Veloso de su álbum homónimo de 1994.
Mr. Darius Teo Joon Aik, a 37-year-old sales professional, decided to pursue a part-time Bachelor of Commerce (Marketing) degree at Curtin Singapore to upgrade his skills. He favors Curtin's structured lessons and assessments that encourage teamwork and ensure students understand course topics. Curtin also accommodates students by not restricting course loads and prioritizing student welfare. While juggling work and study is tiring, Mr. Teo enjoys the social and learning experiences of school. He has already achieved high distinction in several courses and credits his family for their support in helping him succeed academically.
360° Management Consultants helps corporations, governments, and SMEs improve workforce capabilities and organizational performance to positively impact business results. They offer workforce development consulting to define job structures, evaluate employee alignment, and measure performance to drive business execution. Their unique workforce assessments examine individual employee characteristics and experiences to better align each person's skills and perspectives with organizational needs. They can help companies successfully restructure and realign their workforce when needed to reduce costs, improve operations, ensure growth, and achieve a positive return on investment.
The document discusses the applicability of Indian transfer pricing regulations to guarantee transactions between multinational companies and their subsidiaries. It summarizes two key judicial precedents on this issue:
1) The Delhi Tribunal in Bharti Airtel v. Addl. CIT held that issuing a corporate guarantee is not an "international transaction" as it does not impact the issuer's profits, income, losses or assets.
2) However, the Hyderabad Tribunal in a recent Four Soft case held that corporate guarantees do fall under the definition of "international transaction" after a 2012 amendment. While the guarantee must be priced, the Tribunal said a bank guarantee cannot be used as a comparable benchmark for pricing corporate
Este documento lista dos canciones musicales: "Quiet Nights of Quiet Stars (Corcovado)" interpretada por Ella Fitzgerald en su álbum de 2003 "Ella abraça Jobim", y "Are You Havin ́ Any Fun?" interpretada por Elaine Stritch en su álbum de 2015 "Getting into the Habit".
Folha 325 mãozinha quase milagrosa na colheita do caféThiago Tavares
[1] As derriçadeiras motorizadas substituíram a colheita manual do café de forma eficiente, permitindo que um operador colha tanto quanto 2-4 colhedores manuais. [2] Inicialmente houve desconfiança no maquinário, mas ele vem sendo continuamente aprimorado. [3] As derriçadeiras beneficiaram tanto os cafeicultores, que podem colher suas lavouras com menos trabalhadores, quanto os próprios colhedores, que aumentaram sua renda.
Manual de estúdio é um livro dedicado a pessoas interessadas em montar seu home studio, ou simplesmente obter conhecimento sobre técnicas e equipamentos utilizados em home studio, livro muito bom para iniciantes sobre o tema sonoridade.
Este documento presenta un cuadro comparativo de los conceptos de objetivo, propósito y competencia. Define objetivo como un planteamiento de una meta o propósito a alcanzar, y da ejemplos como "comprobar" o "conocer". Define propósito como un objetivo específico, dando como ejemplo "elegir un representante". Finalmente, define competencia como los conocimientos, habilidades y destrezas que una persona desarrolla para funcionar en el mundo, dando como ejemplos competencias comunicativas o matemáticas.
This document summarizes a webinar about cybersecurity for power grids. It introduces OPAL-RT, a company that provides real-time digital simulators for power systems. It then discusses how modern power grids are vulnerable to cyberattacks as they incorporate more intelligent technologies. The rest of the webinar focuses on how real-time simulation can be used to assess cybersecurity risks, research attack mitigation systems, and test compliance with new standards. Speakers from OPAL-RT and the Pacific Northwest National Laboratory discuss their work using real-time simulation for cybersecurity applications.
The document discusses the costs of achieving FedRAMP certification for cloud service providers (CSPs). It summarizes that:
1) Recent reports have cited costs of $4-5 million on average, but these were based on only a few CSPs and may not be accurate or representative.
2) The certification process through a third-party assessment organization (3PAO) like Veris Group typically costs $150,000-$200,000, with additional costs for advisory services, continuous monitoring, and annual recertification.
3) While certification is not cheap, when done efficiently it should not cost millions and is important for CSPs to gain federal contracts and comply with government security standards.
The document provides information on performing and interpreting an ultrasound of the liver. It discusses normal liver anatomy and Doppler assessments of the hepatic vessels. Key findings of a normal liver ultrasound include evaluating the size, shape, echogenicity and echotexture of the liver. Doppler ultrasound can assess blood flow in the hepatic arteries, portal veins and hepatic veins which branch throughout the liver and should demonstrate continuous flow in the expected directions. Spectral analysis of waveforms can help identify abnormalities associated with conditions like portal hypertension.
The document discusses several areas of progress and potential in nanotechnology, as well as some pitfalls. It describes advances in zirconium isotope separation that could improve nuclear reactor components. It highlights the development of institutes studying nanoscience, like the National Institute for Nanotechnology and Institute for Quantum Computing. It also outlines potential applications of nanotechnology in areas like molecular electronics, quantum computing, biomedical imaging, and targeted drug delivery.
The document summarizes recent developments in optical and photonic technology at Zhejiang University's Department of Optical Engineering. It discusses research on micro- and nano-fibers, photonic crystals, optical thin film devices, and their applications. The department has grown to become a leading institution in China for optical engineering education and research, with over 98 faculty/staff members and extensive funding for projects.
The Bristol Centre for Nanoscience and Quantum Information is a world-leading research center focused on nanoscience and quantum information. It provides a highly specialized facility for researchers with 1620m2 of space including cleanrooms, labs, offices and meeting spaces. Current research at the center includes nanomaterials, quantum photonics, nanotoxicology and more. The center also coordinates doctoral training and collaborations to maximize its impact on nanotechnology research.
Design and development of solar pumped Nd:YAG Laserajay singh
This document presents the design and development of a solar pumped Nd:YAG laser system. It discusses the motivation for using sunlight as the pumping source instead of traditional power supplies. The basic design of the system includes a Fresnel lens for solar concentration, a light guide to transport the sunlight, a laser cavity with Nd:YAG laser rod, and an output coupler. Characterization of the laser rod and other components is also presented. Experimental results show emission spectra when pumping with both solar energy and an 808 nm diode laser. Future applications of this prototype solar laser system include material processing, sensing, and deep space communications.
1) The document discusses ultrashort pulse (USP) laser interactions with matter, including microresonator-based optical frequency combs, high peak power laser processing of materials, and extreme ultraviolet comb spectroscopy.
2) It outlines several research initiatives exploring topics like dynamics of microresonator comb generation, laser ablation mechanisms with ultrashort pulses, and dual comb spectroscopy in the extreme ultraviolet.
3) The document also covers applications of USP lasers in metrology, material science, and particle acceleration, and research into relativistic laser-matter interactions generating bright x-ray sources.
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1. Replacing lead in hybrid perovskite
for more sustainable optoelectronics
Kyle Miller
Home Institution: University of Puget Sound
MRSEC Faculty Advisor: Prof. Russell Holmes
Graduate Student Advisor: Catherine Clark
2. What is perovskite?
Green, Martin A, et al. “The Emergence of Perovskite Solar Cells.” Nat Photon 8.7 (2014): 506–514. Web.
3. What is hybrid perovskite?
Organic
Inorganic
Green, Martin A, et al. “The Emergence of Perovskite Solar Cells.” Nat Photon 8.7 (2014): 506–514. Web.
4. Why perovskite?
National Center for Photovoltaics. "Best Research-Cell Efficiencies." National Renewable Energy Laboratory
(2016)
5. Issues with Perovskite
Dominant Device Architecture: Methylammonium lead triiodide
(CH3NH3PbI3)
Environmental
Health and Safety
Hazards of Lead
Lead Mining and
Processing
Chemical Instability
Commercialization
Inhibitors Negative PR for
lead content
12. Sealing Films between Substrates
Spin-coated film sealed between
two quartz substrates with epoxy
Cross section of side view
UV-cured Epoxy
Spin-coated film
Quartz substrate
29. Conclusion
• Did not confirm Kumar findings
• Unstable films
• PL and UV-Vis data showed no significant difference
between the BaI2 + MAI and BaI2 only solutions
• XRD patterns* did not show perovskite peaks
*XRD was performed by Catherine Clark.
30. Further Research
• Continue solid-phase (crystalline films) characterization
• Re-attempt Kumar experiment with published paper
• Explore alternatives:
• Barium precursors (BaI2 Ba(OAc)2, Ba(NO3)2)
• Halogens (CH3NH3BaI3 CH3NH3BaCl3, CH3NH3BaBr3)
• Synthesis methods (solutions process vapor deposition)
• Solvents (DMF DMSO, GBL, DMAc)
31. Acknowledgements
• Catherine Clark
• Professor Russell Holmes
• Holmes Group
• This work was supported primarily by the National Science
Foundation MRSEC and REU programs under Award Numbers
DMR-1263062 & DMR-1420013
Editor's Notes
Introduce self
I had the pleasure this summer of working with Catherine Clark and Professor Russ Holmes
Today I’ll be talking to you
A perovskite is a crystal with the formula ABX3 where A and B are large…
In this study we look specifically at a hybrid perovskite which has an organic A cation and inorganic B and X ions.
In terms of power conversion efficiency, perovskite solar cells are currently the fastest-improving architecture in modern photovoltaics. Since 2006, perovskite photovoltaic cells have experienced an unprecedented increase from 2.2% to 22.1% power conversion efficiency, now rivaling more established architectures such as CdTe (NREL 2016)
However, there are some serious issues
Our society is phasing out lead due to its environmental health and safety concerns, so it is a serious inhibitor to commercialization.
- Moreover these films are moisture-sensitive and fall apart in humid air, making it more difficult to construct robust devices fit for consumer use.
Considering these difficulties, it would be very useful to find a replacement for lead that would prove less problematic for large-scale, consumer-oriented devices.
There has been a lot of talk in literature about the potential of barium
Furthermore the manuscript claims that the perovskite synthesized has a wide bandgap (which makes it transparent to visible light) and is stable in ambient conditions.
Ultimately, the manuscript describes a material that would serve as an excellent transparent conducting layer in not just solar cells, but things like touchscreens and LEDs as well.
Our project seeks to replicate the Kumar manuscript and replace lead with barium, to obtain what could be a more stable, environmentally friendly perovskite.
Our main synthesis method is the solution process. Here we mix iodide salts of the B cation and methylammonium and then dissolve in a common organic solvent, dimethylformamide, or DMF. This solution is stirred and heated for 12 hours for complete dissolution. Interestingly, the Kumar paper also noted that the solution had to sit in a vial for a full week before any of the perovskite features showed up in their characterization efforts.
Since some characteristics, namely crystal structure, are most easily probed when a material is in a solid phase, we prepare thin films of our material by spin coating on quartz substrates. Our spin coater spins the substrate at a few thousand rpms and then I drop the solution onto the substrate as it spins. As the centrifugal effect pushes the solution toward the outside and off the substrate, a layer of solute is left behind. That layer is what we would hope to be a film of perovskite.
However, issues quickly surfaced after we started spin
Now this wouldn’t be a problem if we were synthesizing the perovskite described in the Kumar manuscript. But after our first few films ended up looking like this one which turned to liquid despite our sealing efforts, it became quite obvious that we had a different material on our hands.
We tried several methods of preventing air-exposure and this is one method that was sometimes effective but inconsistent. By sandwiching the film between two quartz substrates and sealing the edges with epoxy, we can place the films in the characterization machines usually without exposing the film to air and since quartz absorbs almost no light in the visible spectrum, our photons of interest are free of attenuation. However, our data on the films was not ready in time for this presentation. Thus, all of the following data is from solutions.
MAKE NOTE OF THE POSSIBLITY OF IN-SOLUTION TRANSFORMATIONS – mention the time required in solution for perovskite to form
In this project, I performed 2 types of characterization. The first, ultraviolet-visible absorption spectroscopy, tells us the range of photon energies that the material most efficiently absorbs.
Photoluminescence spectroscopy tells us what the material does with the photons after they are absorbed. Both of these spectroscopies allow us to interrogate the bandgap of the material, which is the energy difference between the top of the valence band and the bottom of the conduction band *point out the band gap*. Photons with energy equal to or greater than the band gap can be absorbed by an electron in the valence band. This electron is then promoted to the conduction band, allowing for more efficient charge transfer. After some time, this electron will fall back down to the valence band and emit a photon with an energy about equal to the band gap. Knowing about a material’s band gap is useful on its own because it can help us determine potential applications of a material, but it will also help us determine if our data corroborates the findings of the Kumar paper, which found a direct bandgap of 3.87 eV.
Here is the UV-Vis spectrum for the MAI and barium iodide solution, to corroborate the Kumar manuscript, we would need to see an absorption peak at 320 nm. Instead, the spectrum is relatively featureless aside from the peak at low wavelengths.
This peak, however is simply the absorption of our solvent, DMF.
After subtracting the DMF background, we see that there is little to no absorption by our solution. So far it looks like we do not have any material that could be photonically interesting.
However, after inadvertently leaving some of the solution in a vial with a bad seal, we discovered that the solution turned yellow. While this was not described at all in the Kumar manuscript, we decided to further characterize the solutions transformation.
- Don’t know if the paper’s solution had air-exposure and there was never a mention of solution color
This is a set of absorption spectra taken at intervals over the time it took for the solution to complete the majority of its color change. We can immediately see a gradual transformation occurring in solution, with our peak increasing over time, eventually maxing out the detector and merging with the DMF absorbance peak.
Here is the same set of spectra after the DMF background has once again been subtracted. Now we notice that there is what looks like another peak around 300nm. It is important to note that this peak is right on the edge of the DMF absorption peak so there is a significant chance that it might be the product of the saturation that occurs due to the DMF absorption. This makes it impossible to get an accurate sense of
Here is the same plot again with the x-axis zoomed in on the peaks. To make the graphical interpretation easier, I have highlighted the peaks that we see on this graph on all of the following graphs.
Taking a look at the emission spectrum, we immediately notice that we have a very broad, messy peak which over time, diminishes and thins on the left side to leave a peak at around 475nm. This emission decrease, in conjunction with the increase in absorbance we saw earlier indicate that the compound being formed in the transformation is an ineffective emitter, undergoing more non-radiative transitions to compensate for the decrease in emission.
Overlaying the absorption peak, we can see that the orange area does not overlap with the main peak at 475nm, indicating that our material is not emitting the same light that it had absorbed. This directly contradicts the claims of the Kumar et al. paper which reported a direct bandgap, which would require a material to emit light that was much closer to its absorption peak.
That possibility is on shaky ground with this photoluminescence excitation scan. With this type of scan, we hope to see our absorption peak line up with the peak on this graph, indicating that the photons being most effectively absorbed are also being most effectively emitted. Instead, this graph shows that only the very red edge of the absorption peak is being efficiently reemitted. This kind of deviation is quite abnormal and further investigation would be needed to find out why this occurs. Now at this point, we are quite eager to know what part of our solution is causing this transformation.
Well after we took enough data with the PL machine to be moderately confident that this shape is not an artifact of the machine itself, we can say that the removal of MAI does not appear to adversely affect the transformation we observed in the solution. The slightly inconsistent amplitudes can be attributed to small differences in concentrations of the solution.
Here with more comparison, this time with excitation scans, you’ll notice that there is a small difference at 340 nm, but the vast majority of the change seems to be independent of the MAI.
Our absorption data also confirmed this explanation.
As you can see, the solution made without MAI undergoes a very similar transformation. This means that the transformation observed in the air-exposed solution is likely just an interaction with an air-borne compound and the highly reactive barium iodide precursor, it could also be a reaction with the solvent or even a solvent complexation facilitated by something in the air but those are a bit far-fetched. Ultimately, since methylammonium is required for the formation of the target perovskite, we can be fairly certain that this is not that perovskite.
Ultimately, we did not confirm the findings of the Kumar et al. manuscript:
Their films were air-stable and our films quickly liquefied in ambient conditions
Our photoluminescence and uv-vis data showed only very small differences between the barium iodide solution with methylammonium iodide and the one without, indicating that there was likely no reaction occurring between the two and thus no perovskite formation
Furthermore, our XRD data, which was not shown in this presentation and was taken by my mentor Catherine showed none of the peaks reported by the Kumar et al manuscript
Looking forward,
Since we have not comprehensively characterized films of this solution, it would be valuable to continue pursuing that part of the project since some perovskites indeed do not form until they are brought into solid phase.
Since the Kumar et al. work was still a manuscript and lacked some of the useful information describing their methods, it would make sense to reattempt to replicate their experiment once the full paper is published
In the mean time, there are plenty of variables to explore which are well-documented for lead and tin perovskites such as our precursor and the halogen used, both of which were iodine in our experiment, our synthesis method, and our solvent.
I’d like to thank the Holmes research group and Catherine in particular for being a bottomless source of advice, friendliness, and patience.
I’d like to thank Professor Holmes for always being ready to offer his expertise and guidance to not only this project but my life aspirations as well, and the NSF and MRSEC programs for providing me with this opportunity.