Pinhole-free perovskite films for efficient solar modules

We report on a perovskite solar module with an aperture area of 4 cm2 and geometrical fill factor of 91%. The module exhibits an aperture area power conversion efficiency (PCE) of 13.6% from a current–voltage scan and 12.6% after 5 min of maximum power point tracking. High PCE originates in pinhole-free perovskite films made with a precursor combination of Pb(CH3CO2)2·3H2O, PbCl2, and CH3NH3I

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

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

Multijunction Solar Cells Based on Hybrid Perovskites

We investigate the efficiency potential of organic-inorganic halide perovskite/c-Silicon tandem solar cells, a new class of photovoltaic devices. Tandem solar cells constructed from a crystalline Silicon bottom cell and a low-cost top cell offer a promising way to ensure long-term price reductions through high efficiency photovoltaic modules. We are currently working on developing a bifacial thin-film top cell with an organic-inorganic semiconductor material having a bandgap greater than 1.6 eV. Methylammonium Lead trihalide has proved to be a promising material for the top cell. It can be solution-processed and allows for bandgap tuning by varying the halide concentration. The bandgap of the top cell will be tuned such that it can be adapted in a tandem configuration along with a crystalline Silicon bottom cell. With the tandem configuration of perovskite/c-Si solar cells, we aim to cross the 25% power conversion efficiency barrier in order to deliver solutions for high-performance applications.status: publishe

Permissions Based Android Vulnerability Detection and Classification Based on Severity Using Machine Learning

With the sudden upswing in digitization, usage of Android smartphones has evidently become conventional and common. Nevertheless, such extensive popularity of Android systems comes with a major trade-off between usage and security. Time and again, it has been proven that the existence of malicious applications leverage permissions given by the Android systems in order to compromise them. However, there exist certain combinations of permission sets that could potentially lead to such attacks. To address this, we propose a two-layer architecture, where each layer has an implicit handshake with a Machine Learning ensemble model, that aims at vulnerability detection as well as classification of these detected vulnerabilities into one among the three levels of severity – High Risk, Medium Risk and Low Risk. Efficiency of the proposed system has been evaluated against existing Machine Learning based models such as K-Nearest Neighbors (KNN), Decision Tree Algorithms and Multi-Layered Perceptron (MLP) on an Android Permission-Based Dataset. Results show that our proposed model outperforms the existing approaches, which has been quantitatively evaluated using accuracy and F1-score.</jats:p

Effects of solar irradiation and nitrate on dissolved organic matter and freshwater bacterioplankton

In surface waters, solar radiation transforms complex dissolved organic compounds into photoproducts that are more readily available for bacterial metabolic use. In this way, photochemical processes can influence both carbon cycling and freshwater bacterioplankton communities. We experimentally studied photochemical transformation of dissolved organic carbon (DOC) in the presence or absence of nitrate added as a photosensitizer and followed how this affected growth and community composition of heterotrophic bacteria. As expected, bleaching of chromophoric dissolved organic matter (cDOM) was strongly positively correlated to total energy content of the solar irradiance. In contrast, the addition of nitrate had no significant impact on neither DOC photodegradation or bleaching. Bacterial growth assays revealed extensive solar-driven transformation of biologically recalcitrant carbon compounds into more labile forms that led to enhanced bacterial growth. Based on 16S rRNA community analyses applied to regrowth cultures, we demonstrate that solar exposure and to a lesser extent also the nitrate-mediated photosensitization, had a significant influence on the taxonomic composition of bacterioplankton communities. All communities were dominated by class Proteobacteria, and notably known bacterivorous taxa such as Bdellovibrio and like organisms (BALOs) within the class of Oligoflexia were strongly favored by DOM exposed to solar irradiation while this effect was not seen when irradiation was combined with nitrate as photosensitizer. In addition, taxa which seem to have a copiotrophic lifestyle such as Acin (Gammaproteobacteria) showed a positive response to the irradiation and nitrate addition while the opposite was found for LD12, acI-A and alfVI that are considered to have a more oligotrophic one. Further, ambiguous responses from the treatments were observed as bal-A1 (FukuN47) belonging to Bacteroidetes only responded positively to the irradiation in the absence of nitrate. We conclude that photochemical transformation of DOM does not only influence the energy transfer through the microbial food web, but may also cause cryptic changes in microbial community structure which may result in functional shifts in the bacterioplankton.</p

Food Safety on the Farm: Good Agricultural Practices and Good Handling Practices – Water

Good agricultural practices (GAPs) and good handling practices (GHPs) encompass the general procedures growers, packers, and processors of fresh fruits and vegetables should follow to ensure the safety of their product. GAPs usually address preharvest practices (i.e., in the field), while GHPs cover postharvest practices, including packing and shipping. This 7-page fact sheet covers GAPs and GHPs relating to water use. This major revision is a part of the Food Safety on the Farm series and was written by Jaysankar De, Christopher R. Pabst, Jessica Lepper, Renée Goodrich-Schneider, and Keith R. Schneider and published by the UF/IFAS Food Science and Human Nutrition Department. http://edis.ifas.ufl.edu/fs136</jats:p

Food Safety on the Farm: Good Agricultural Practices and Good Handling Practices –Traceback

Good Agricultural Practices (GAP) and Good Handling Practices (GHP) are voluntary audits that verify fruits and vegetables are produced, packed, handled, and stored as safely as possible to keep the risks of microbial food safety hazards at the minimal level. Good Agricultural Practices usually deal with preharvest practices (i.e., in the field), while GHPs cover postharvest practices, including packing and shipping. This 3-page fact sheet in the Food Safety on the Farm series covers GAPs and GHPs relating to traceback, or the ability to track food items, such as fresh produce, back to their source. This major revision was written by Jaysankar De, Christopher R. Pabst, Alexandra S. Chang, Renée M. Goodrich-Schneider, and Keith R. Schneider and published by the UF/IFAS Food Science and Human Nutrition Department. http://edis.ifas.ufl.edu/fs15

Food Safety on the Farm: Good Agricultural Practices and Good Handling Practices – Water

Good agricultural practices (GAPs) and good handling practices (GHPs) encompass the general procedures growers, packers, and processors of fresh fruits and vegetables should follow to ensure the safety of their product. GAPs usually address preharvest practices (i.e., in the field), while GHPs cover postharvest practices, including packing and shipping. This 7-page fact sheet covers GAPs and GHPs relating to water use. This major revision is a part of the Food Safety on the Farm series and was written by Jaysankar De, Christopher R. Pabst, Jessica Lepper, Renée Goodrich-Schneider, and Keith R. Schneider and published by the UF/IFAS Food Science and Human Nutrition Department. http://edis.ifas.ufl.edu/fs13