The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Henry J Snaith - One of the best experts on this subject based on the ideXlab platform.
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enhancement of perovskite based solar cells employing core shell metal nanoparticles
Nano Letters, 2013Co-Authors: Wei Zhang, Michael Saliba, Samuel D Stranks, Ulrich Wiesner, Yao Sun, Xian Shi, Henry J SnaithAbstract:Recently, inorganic and hybrid light absorbers such as quantum dots and Organometal halide perovskites have been studied and applied in fabricating thin-film photovoltaic devices because of their low-cost and potential for high efficiency. Further boosting the performance of solution processed thin-film solar cells without detrimentally increasing the complexity of the device architecture is critically important for commercialization. Here, we demonstrate photocurrent and efficiency enhancement in meso-superstructured Organometal halide perovskite solar cells incorporating core-shell Au@SiO2 nanoparticles (NPs) delivering a device efficiency of up to 11.4%. We attribute the origin of enhanced photocurrent to a previously unobserved and unexpected mechanism of reduced exciton binding energy with the incorporation of the metal nanoparticles, rather than enhanced light absorption. Our findings represent a new aspect and lever for the application of metal nanoparticles in photovoltaics and could lead to facile tuning of exciton binding energies in perovskite semiconductors.
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enhancement of perovskite based solar cells employing core shell metal nanoparticles
Nano Letters, 2013Co-Authors: Wei Zhang, Michael Saliba, Samuel D Stranks, Ulrich Wiesner, Henry J SnaithAbstract:Recently, inorganic and hybrid light absorbers such as quantum dots and Organometal halide perovskites have been studied and applied in fabricating thin-film photovoltaic devices because of their low-cost and potential for high efficiency. Further boosting the performance of solution processed thin-film solar cells without detrimentally increasing the complexity of the device architecture is critically important for commercialization. Here, we demonstrate photocurrent and efficiency enhancement in meso-superstructured Organometal halide perovskite solar cells incorporating core–shell Au@SiO2 nanoparticles (NPs) delivering a device efficiency of up to 11.4%. We attribute the origin of enhanced photocurrent to a previously unobserved and unexpected mechanism of reduced exciton binding energy with the incorporation of the metal nanoparticles, rather than enhanced light absorption. Our findings represent a new aspect and lever for the application of metal nanoparticles in photovoltaics and could lead to facil...
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Efficient Organometal trihalide perovskite planar-heterojunction solar cells on flexible polymer substrates.
Nature communications, 2013Co-Authors: Pablo Docampo, Mariam Darwich, James M. Ball, Giles E. Eperon, Henry J SnaithAbstract:Organometal trihalide perovskite solar cells offer the promise of a low-cost easily manufacturable solar technology, compatible with large-scale low-temperature solution processing. Within 1 year of development, solar-to-electric power-conversion efficiencies have risen to over 15%, and further imminent improvements are expected. Here we show that this technology can be successfully made compatible with electron acceptor and donor materials generally used in organic photovoltaics. We demonstrate that a single thin film of the low-temperature solution-processed Organometal trihalide perovskite absorber CH3NH3PbI3-xClx, sandwiched between organic contacts can exhibit devices with power-conversion efficiency of up to 10% on glass substrates and over 6% on flexible polymer substrates. This work represents an important step forward, as it removes most barriers to adoption of the perovskite technology by the organic photovoltaic community, and can thus utilize the extensive existing knowledge of hybrid interfaces for further device improvements and flexible processing platforms.
Qinye Bao - One of the best experts on this subject based on the ideXlab platform.
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Oxygen- and Water-Induced Energetics Degradation in Organometal Halide Perovskites.
ACS applied materials & interfaces, 2018Co-Authors: Jianming Yang, F. Gao, Jian-xin Tang, Zhongcheng Yuan, Xianjie Liu, Slawomir Braun, Chun-gang Duan, Mats Fahlman, Qinye BaoAbstract:Organometal halide perovskites are under rapid development, and significant focus has been placed on their stability that currently presents a major obstacle for practical application. Energetics plays a vital role in charge injection/extraction and transport properties in devices. Here, we in situ investigate oxygen- and water-induced energetics degradation in Organometal halide perovskite films. Oxygen gas induces an upward shift of the vacuum level of the perovskite films because of the formation of an oxygen-induced surface dipole, water vapor causes a significant vacuum-level downshift, and the valence band binding energy referenced to the Fermi level simultaneously increases so as to keep the ionization potential of the perovskite films unchanged. Moreover, the chemical compositions, crystalline structures, surface morphologies, and dynamical properties also are monitored and analyzed in detail. These results are indispensable to understand the degradation mechanisms and to perform the optimizations...
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In Situ Observation of Light Illumination-Induced Degradation in Organometal Mixed-Halide Perovskite Films.
ACS applied materials & interfaces, 2018Co-Authors: Teng‐yu Jin, Yue-qi Liu, Qinye Bao, Conor O'carroll, Jian-xin TangAbstract:Organometal mixed-halide perovskite materials hold great promise for next-generation solar cells, light-emitting diodes, lasers, and photodetectors. Except for the rapid progress in the efficiency of perovskite-based devices, the stability issue over prolonged light illumination has severely hindered their practical application. The deterioration mechanism of Organometal halide perovskite materials under light illumination has seldom been conducted to date, which is indispensable to the understanding and optimization of photon-harvesting process inside perovskite-based optoelectronic devices. Here, explicit degradation pathways and comprehensive microscopic understandings of white-light-induced degradation have been put forward for two Organometal mixed-halide perovskite materials (e.g., MAPbI3–xClx and MAPbBr3–xClx) under high vacuum conditions. In situ compositional analysis and real-time film characterizations reveal that the decomposition of both mixed-halide perovskites starts at the grain boundaries...
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In Situ Observation of Light Illumination-Induced Degradation in Organometal Mixed-Halide Perovskite Films
2018Co-Authors: Teng-yu Jin, Yue-qi Liu, Qinye Bao, Conor O’carroll, Jian-xin TangAbstract:Organometal mixed-halide perovskite materials hold great promise for next-generation solar cells, light-emitting diodes, lasers, and photodetectors. Except for the rapid progress in the efficiency of perovskite-based devices, the stability issue over prolonged light illumination has severely hindered their practical application. The deterioration mechanism of Organometal halide perovskite materials under light illumination has seldom been conducted to date, which is indispensable to the understanding and optimization of photon-harvesting process inside perovskite-based optoelectronic devices. Here, explicit degradation pathways and comprehensive microscopic understandings of white-light-induced degradation have been put forward for two Organometal mixed-halide perovskite materials (e.g., MAPbI3–xClx and MAPbBr3–xClx) under high vacuum conditions. In situ compositional analysis and real-time film characterizations reveal that the decomposition of both mixed-halide perovskites starts at the grain boundaries, leading to the formation of hydrocarbons and ammonia gas with the residuals of PbI2(Cl), Pb, or PbClxBr2–x in the films. The degradation has been correlated to the localized trap states that induce strong coupling between photoexcited carriers and the crystal lattice
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Oxygen- and Water-Induced Energetics Degradation in Organometal Halide Perovskites
2018Co-Authors: Jianming Yang, F. Gao, Jian-xin Tang, Zhongcheng Yuan, Xianjie Liu, Slawomir Braun, Chun-gang Duan, Mats Fahlman, Qinye BaoAbstract:Organometal halide perovskites are under rapid development, and significant focus has been placed on their stability that currently presents a major obstacle for practical application. Energetics plays a vital role in charge injection/extraction and transport properties in devices. Here, we in situ investigate oxygen- and water-induced energetics degradation in Organometal halide perovskite films. Oxygen gas induces an upward shift of the vacuum level of the perovskite films because of the formation of an oxygen-induced surface dipole, water vapor causes a significant vacuum-level downshift, and the valence band binding energy referenced to the Fermi level simultaneously increases so as to keep the ionization potential of the perovskite films unchanged. Moreover, the chemical compositions, crystalline structures, surface morphologies, and dynamical properties also are monitored and analyzed in detail. These results are indispensable to understand the degradation mechanisms and to perform the optimizations of stable materials and devices in the future
Alfred V Hirner - One of the best experts on this subject based on the ideXlab platform.
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Toxicity of Organometal(loids)
Journal of toxicology, 2012Co-Authors: Elke Dopp, Alfred V Hirner, Shelley Bhattacharya, Michael Aschner, Tanja SchwerdtleAbstract:Biomethylation of metals and metalloids is a process ubiquitously occurring in the environment (under aerobic and anaerobic conditions), which leads to the formation of chemical species with significantly higher mobility and altered toxicity. The alkylation of inorganic metal(loid)s through transfer, for example, of methyl groups, is a significant factor in the biogeochemical cycling of the metal(loid) elements. Biomethylation has been described in natural systems for arsenic, cadmium, germanium, mercury, sulfur, antimony, selenium, tin, tellurium, and lead as well as for bismuth, gold, chromium, palladium, platinum, and thallium under laboratory conditions. In this special issue biomethylation products of arsenic, bismuth, mercury, lead, and tin are of special interest. Of all metal(loid) species in environmental systems, the element arsenic received the greatest attention worldwide. In this issue, recent research on influences of arsenic methylation on toxicity of arsenic species (M. Hall and M. Gamble), modes of action of arsenic metabolites in human cells (Bartel et al.), and the toxicity of volatile arsenic species compared to volatile species of bismuth, mercury, and tin (E. Dopp et al.) will be presented. Anthropogenic water pollution by butyltin biocides is a well-documented and a severe environmental problem. Its distribution and accumulation in aquatic organisms and also within the food chain leads to biological effects in different organisms. The immunotoxic effects in mammalian cells is highlighted in this special issue by H. Krug. Beside carcinogenic and immunotoxic effects, Organometal(loid)s can exert neurotoxicity. The best known neurotoxic metal(loid) is methylmercury (MeHg). MeHg affects both, the developing and the mature central nervous systems. Several epidemics resulting from the consumption of food contaminated by MeHg have shown the disastrous effects on living organisms. Mechanisms associated with MeHg exposure and neurotoxic effects are described by P. Kaur et al. in this issue. It has to be considered that humans not only are exposed to metal(loid) compounds from the environment via inhalation and ingestion, but may also be able to generate these species by endogenous enzymes or/and biomethylation in the colon. Methanoarchaea have an outstanding capability to methylate numerous metal(loid)s therefore producing toxic and highly mobile derivatives which might influence human health. Interesting studies in this field were carried out by the group of R. Hensel and new results are presented in this issue by B. Bialek et al. and B. Huber et al. Metal(loid)-induced health effects, including carcinogenesis and neurodegeneration, have been reported in numerous publications. However, organisms and cells have developed protective mechanisms to deal with metal(loid) exposure. An overview about mechanisms involved in cellular detoxification of different metals is given in the review of E. Martinez-Finley and M. Aschner. Protein binding of metal(loid)s is also a possibility to detoxify serveral species, for example, lead. This process is highlighted in the review of H. Gonick. Altogether, this special issue addresses contemporary concentrations of Organometal(loids) increasing in dangerous proportions in our environment. Unknowingly, the human population is exposed to such insults, which on the long run may be a point of no return. It is true that there are mechanisms of detoxification which allow the biological systems to survive healthily. In spite of such innate mechanisms of combating stress, there is an urgent global need to realize the portent of environmental disaster staring at our face. Sooner we heed to the indications spelt out in this special issue better it is for the future of mankind. Elke Dopp Shelley Bhattacharya Alfred V. Hirner Michael Ashner Tanja Schwerdtle
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Particle size distribution of Organometal(loid) compounds in freshwater sediments
Applied Organometallic Chemistry, 2007Co-Authors: Lars Duester, L M Hartmann, Lisa Luemers, Alfred V HirnerAbstract:The aim of this study was to determine to what extent particle size determines the occurrence of Organometal(loid) compounds of the elements As, Sb, Sn and Te in freshwater sediments. In addition, the anthropogenic impact upon the distribution through differing usage of freshwater habitats was examined vis-a-vis flowing water, fish farms and a maturation pond for the bio-treatment of wastewater. All habitats sampled were located in the basin of the river Ruhr, Germany. In addition to the detection of high concentrations of total metal(loid) content of As, Sb, Sn and Te in the maturation pond sediments, this habitat also possessed the highest concentration of Organometal(loid) species. Interestingly, the concentration of monomethylated metal(loid)s was up to 100-fold higher than those of higher methylated species of the same element. A maximum of 28 µg kg−1 MMAs, 18 µg kg−1 MMSb and 8 µg kg−1 MMSn per dry weight was detected. A similar tendency was noted for all other freshwater habitats tested. In contrast to methylated arsenic (arsenic containing pesticides are banned in Germany) and antimony species, there is no doubt that the alkyltin species detected, e.g. MBSn and DBSn, are of anthropogenic origin since biogenesis of these species does not occur. Alkyltins are, however, known to enter the environment in a continuous and diffuse manner via discharge to sewage and air. In samples from the maturation pond concentrations of up to 86 and 11 µg kg−1 per dry weight were detected for MBSn and DBSn, respectively. The detection of methylated arsenic and antimony species indicates that biotransformation of these elements is occurring in freshwater habitats. Irrespective of the usage and (anthropogenic) demands on the freshwater habitats tested, the highest concentration of Organometal(loid) species was always detected in the sediment fractions that contained the highest concentration of humic substances and comprised up to 40% clays and silt particles (
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environmental distribution analysis and toxicity of Organometal loid compounds
Critical Reviews in Toxicology, 2004Co-Authors: Elke Dopp, L M Hartmann, Ana Maria Florea, Albert W Rettenmeier, Alfred V HirnerAbstract:The biochemical modification of the metals and metalloids mercury, tin, arsenic, antimony, bismuth, selenium, and tellurium via formation of volatile metal hydrides and alkylated species (volatile and involatile) performs a fundamental role in determining the environmental processing of these elements. In most instances, the formation of such species increases the environmental mobility of the element, and can result in bioaccumulation in lipophilic environments. While inorganic forms of most of these compounds are well characterized (e.g., arsenic, mercury) and some of them exhibit low toxicity (e.g., tin, bismuth), the more lipid-soluble Organometals can be highly toxic. Methylmercury poisoning (e.g., Minamata disease) and tumor development in rats after exposure to dimethylarsinic acid or tributyltin oxide are just some examples. Data on the genotoxicity (and the neurotoxicity) as well as the mechanisms of cellular action of Organometal(loid) compounds are, however, scarce. Many studies have shown that the production of such Organometal(loid) species is possible and likely whenever anaerobic conditions (at least on a microscale) are combined with available metal(loid)s and methyl donors in the presence of suitable organisms. Such anaerobic conditions can exist within natural environments (e.g., wetlands, pond sediments) as well as within anthropogenic environmental systems (e.g., waste disposal sites and sewage treatments plants). Some methylation can also take place under aerobic conditions. This article gives an overview about the environmental distribution of Organometal(loid) compounds and the potential hazardous effects on animal and human health. Genotoxic effects in vivo and in vitro in particular are discussed.
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identification of organic arsenic tin antimony and tellurium compounds in environmental samples by gc ms
Journal of Molecular Structure, 2003Co-Authors: Jan Kosters, Roland A Diazbone, Britta Planerfriedrich, B Rothweiler, Alfred V HirnerAbstract:Abstract In this study, the potential of GC-MS for structure analysis of Organometal(loid) species of arsenic, tin, antimony and tellurium in environmental samples was investigated. Analytes were ionic Organometal(loid) species from compost samples, which were derivatised with NaBH 4 before introduction into the GC/MS via a purge and trap system, as well as volatile species from hydrothermal gases sampled on SPME-fibres. Several organic species of arsenic, tin, antimony and tellurium were identified. By scanning the chromatogram for typical fragments of organoarsenic compounds seven arsenic species were identified. To our knowledge three of them (diarsine, monomethyl diarsine and dimethylarsenomercaptane) have not been reported in environmental samples so far. To further exclude artefacts being misinterpreted as volatile Organometal(loid)s, measurements of volatile arsenic species naturally occurring in hydrothermal samples with SPME-GC-MS were performed. The determination of dimethylarsenomercaptane in these samples confirms that this compound which was also found after derivatisation of ionic arsenic species is not an artefact. A strategy for the identification of unknown species whose structure cannot be elucidated by library comparison or with the help of isotopic patterns is presented. The necessity of positive identification of unknown species and confirmation of known and assumed compounds for speciation analysis is highlighted and the applicability of quadrupol GC/MS for this purpose is stated.
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Derivatization of Organometal(loid) species by sodium borohydride: Problems and solutions
Journal of Chromatography A, 2001Co-Authors: U. M. Grüter, M Hitzke, J. Kresimon, Alfred V HirnerAbstract:Like other derivatization techniques, hydride generation is a chem. reaction that produces side-reactions leading to anal. problems. Demethylation of dimethylarsinic acid is dependent upon the pH level of the hydride generation reaction mixt. If the reaction mixt. was acidic, then in addn. to Me2AsH, the monomethyl arsenic hydride [MeAsH2] could be detected. Demethylation and also the formation of an unidentified arsenic species were noted when tri-Me arsonic oxide was used as derivatization educt. All of these effects depend on the pH level of the hydride generation mixt. The authors obsd. significant levels of Organometal(loid) species of elements such as Ge, As, Sn, Sb, Hg and Bi in blank hydride generation mixts. The Organometal(loid) contamination was irreproducible even during 1 day using a single soln. of sodium borohydride in deionized water. The Organometal(loid) contamination arises directly from the derivatization agent, sodium borohydride, itself. Use of helium purging and various adsorptive materials to decontaminate the sodium borohydride soln. prior to anal. did not result in a significant decrease in Organometal(loid) contamination levels. Use of a palladium-cluster stabilized with 1,10-phenanthroline as alternative hydride generation derivatization agent was not found to be suitable, since reaction yields were poor and transmethylation reactions were noted.
Hiroshi Segawa - One of the best experts on this subject based on the ideXlab platform.
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Robust PbI6 Framework of Organometal Halide CH3NH3PbI3 Perovskite Observed by High Resolution Transmission Electron Microscopy
Chemistry Letters, 2019Co-Authors: Ludmila Cojocaru, Tae Woong Kim, Satoshi Uchida, Hiroshi SegawaAbstract:Direct observation of the crystal domains of Organometal halide perovskite MAPbI3 (MA: CH3NH3+) was carried out by high resolution transmission electron microscopy (HR-TEM) followed by focused ion ...
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Direct Observation of the Tunneling Phenomenon in Organometal Halide Perovskite Solar Cells and Its Influence on Hysteresis
ACS Energy Letters, 2018Co-Authors: Tae Woong Kim, Satoshi Uchida, Ludmila Cojocaru, Myoung Kim, Hiroshi SegawaAbstract:Recently, Organometal halide perovskites have shown the unprecedented success in solar cell application and attracted widespread attention as next-generation photovoltaic materials. Regardless of the remarkable achievements, the hysteretic behavior of the Organometal halide perovskite solar cells is not fully understood yet, and its origins suggested are still in dispute, even though the hysteresis deteriorates the stability of the perovskite solar cells and, thus, prevents their commercialization. Here we report direct observation of the tunneling phenomenon by using nm-scale in situ current density–voltage characterization and suggest that the tunneling phenomenon can induce hysteresis in the perovskite solar cells. We identified that the tunneling phenomenon originated from the local-heavy doping caused by the electrostatic dipole at a rough interface and that the hysteresis of the perovskite solar cells possibly originated by piling the tunneling currents. This Letter shows a new possible origin of th...
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Direct Observation of the Tunneling Phenomenon in Organometal Halide Perovskite Solar Cells and Its Influence on Hysteresis
2018Co-Authors: Tae Woong Kim, Satoshi Uchida, Ludmila Cojocaru, Myoung Kim, Hiroshi SegawaAbstract:Recently, Organometal halide perovskites have shown the unprecedented success in solar cell application and attracted widespread attention as next-generation photovoltaic materials. Regardless of the remarkable achievements, the hysteretic behavior of the Organometal halide perovskite solar cells is not fully understood yet, and its origins suggested are still in dispute, even though the hysteresis deteriorates the stability of the perovskite solar cells and, thus, prevents their commercialization. Here we report direct observation of the tunneling phenomenon by using nm-scale in situ current density–voltage characterization and suggest that the tunneling phenomenon can induce hysteresis in the perovskite solar cells. We identified that the tunneling phenomenon originated from the local-heavy doping caused by the electrostatic dipole at a rough interface and that the hysteresis of the perovskite solar cells possibly originated by piling the tunneling currents. This Letter shows a new possible origin of the hysteresis and the importance of the interface condition in perovskite solar cells
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Evolution of Organometal halide solar cells
Journal of Photochemistry and Photobiology C: Photochemistry Reviews, 2018Co-Authors: Jotaro Nakazaki, Hiroshi SegawaAbstract:Abstract Emerging Organometal halide solar cells have attracted wide attention as “perovskite solar cells (PSCs)” from very many researchers, and the related articles more than 4000 have been published to date. The power conversion efficiency (PCE) over 22% was achieved within a few years from the advent of the PSCs. In this review article, publications about the PSCs were summarized along their ‘submitted date’, to record the course of the progress. At the first stage, the PSCs were established as nano-structured solar cells. The efficiency up to 15% attracted the researchers in dye-sensitized solar cells and organic thin-film solar cells. After the appearance of planar hetero-junction type PSCs, the power generation mechanism has been argued. Around that time, several issues arose, such as I–V hysteresis and chloride contents. Although there were several severe comments about these issues, the developments of the PSCs progressed steadily, then efficiencies over 20% were reported. At present, the highest PCE in published papers is 22.6%, and the NREL chart records 22.7%. The development history of the PSCs is summarized in this review.
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origin of the hysteresis in i v curves for planar structure perovskite solar cells rationalized with a surface boundary induced capacitance model
Chemistry Letters, 2015Co-Authors: Ludmila Cojocaru, Satoshi Uchida, P V V Jayaweera, Shoji Kaneko, Jotaro Nakazaki, Takaya Kubo, Hiroshi SegawaAbstract:For efficient hybrid solar cells based on Organometal halide perovskites, the real origin of the I–V hysteresis became a big issue and has been discussed widely. In this study, simulated I–V curves...
Wei Zhang - One of the best experts on this subject based on the ideXlab platform.
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enhancement of perovskite based solar cells employing core shell metal nanoparticles
Nano Letters, 2013Co-Authors: Wei Zhang, Michael Saliba, Samuel D Stranks, Ulrich Wiesner, Henry J SnaithAbstract:Recently, inorganic and hybrid light absorbers such as quantum dots and Organometal halide perovskites have been studied and applied in fabricating thin-film photovoltaic devices because of their low-cost and potential for high efficiency. Further boosting the performance of solution processed thin-film solar cells without detrimentally increasing the complexity of the device architecture is critically important for commercialization. Here, we demonstrate photocurrent and efficiency enhancement in meso-superstructured Organometal halide perovskite solar cells incorporating core–shell Au@SiO2 nanoparticles (NPs) delivering a device efficiency of up to 11.4%. We attribute the origin of enhanced photocurrent to a previously unobserved and unexpected mechanism of reduced exciton binding energy with the incorporation of the metal nanoparticles, rather than enhanced light absorption. Our findings represent a new aspect and lever for the application of metal nanoparticles in photovoltaics and could lead to facil...
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enhancement of perovskite based solar cells employing core shell metal nanoparticles
Nano Letters, 2013Co-Authors: Wei Zhang, Michael Saliba, Samuel D Stranks, Ulrich Wiesner, Yao Sun, Xian Shi, Henry J SnaithAbstract:Recently, inorganic and hybrid light absorbers such as quantum dots and Organometal halide perovskites have been studied and applied in fabricating thin-film photovoltaic devices because of their low-cost and potential for high efficiency. Further boosting the performance of solution processed thin-film solar cells without detrimentally increasing the complexity of the device architecture is critically important for commercialization. Here, we demonstrate photocurrent and efficiency enhancement in meso-superstructured Organometal halide perovskite solar cells incorporating core-shell Au@SiO2 nanoparticles (NPs) delivering a device efficiency of up to 11.4%. We attribute the origin of enhanced photocurrent to a previously unobserved and unexpected mechanism of reduced exciton binding energy with the incorporation of the metal nanoparticles, rather than enhanced light absorption. Our findings represent a new aspect and lever for the application of metal nanoparticles in photovoltaics and could lead to facile tuning of exciton binding energies in perovskite semiconductors.