Planar perovskite solar cells (PSCs) made entirely via solution processing at low temperatures (<150°C) offer promise for simple manufacturing, compatibility with flexible substrates, and perovskite-based tandem devices. However, these PSCs require an electron-selective layer that performs well with similar processing. We report a contact-passivation strategy using chlorine-capped TiO2 colloidal nanocrystal film that mitigates interfacial recombination and improves interface binding in low-temperature planar solar cells. We fabricated solar cells with certified efficiencies of 20.1 and 19.5% for active areas of 0.049 and 1.1 square centimeters, respectively, achieved via low-temperature solution processing. Solar cells with efficiency greater than 20% retained 90% (97% after dark recovery) of their initial performance after 500 hours of continuous room-temperature operation at their maximum power point under 1-sun illumination (where 1 sun is defined as the standard illumination at AM1.5, or 1 kilowatt/square meter).

https://science.sciencemag.org/content/sci/early/2017/02/01/science.aai9081.full.pdf

Efficient and stable solution-processed planar perovskite solar cells via contact passivation.

The photovoltaics of organic–inorganic lead halide perovskite materials have shown rapid improvements in solar cell performance, surpassing the top efficiency of semiconductor compounds such as CdTe and CIGS (copper indium gallium selenide) used in solar cells in just about a decade. Perovskite preparation via simple and inexpensive solution processes demonstrates the immense potential of this thin-film solar cell technology to become a low-cost alternative to the presently commercially available photovoltaic technologies. Significant developments in almost all aspects of perovskite solar cells and discoveries of some fascinating properties of such hybrid perovskites have been made recently. This Review describes the fundamentals, recent research progress, present status, and our views on future prospects of perovskite-based photovoltaics, with discussions focused on strategies to improve both intrinsic and extrinsic (environmental) stabilities of high-efficiency devices. Strategies and challenges regardi...

Halide Perovskite Photovoltaics: Background, Status, and Future Prospects

Multi-Criteria Decision Aid (MCDA) or Multi-Criteria Decision Making (MCDM) methods have received much attention from researchers and practitioners in evaluating, assessing and ranking alternatives across diverse industries. Among numerous MCDA/MCDM methods developed to solve real-world decision problems, the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) continues to work satisfactorily across different application areas. In this paper, we conduct a state-of-the-art literature survey to taxonomize the research on TOPSIS applications and methodologies. The classification scheme for this review contains 266 scholarly papers from 103 journals since the year 2000, separated into nine application areas: (1) Supply Chain Management and Logistics, (2) Design, Engineering and Manufacturing Systems, (3) Business and Marketing Management, (4) Health, Safety and Environment Management, (5) Human Resources Management, (6) Energy Management, (7) Chemical Engineering, (8) Water Resources Management and (9) Other topics. Scholarly papers in the TOPSIS discipline are further interpreted based on (1) publication year, (2) publication journal, (3) authors' nationality and (4) other methods combined or compared with TOPSIS. We end our review paper with recommendations for future research in TOPSIS decision-making that is both forward-looking and practically oriented. This paper provides useful insights into the TOPSIS method and suggests a framework for future attempts in this area for academic researchers and practitioners.

Review: A state-of the-art survey of TOPSIS applications

The validity of the cubic law for laminar flow of fluids through open fractures consisting of parallel planar plates has been established by others over a wide range of conditions with apertures ranging down to a minimum of 0.2 µm. The law may be given in simplified form by Q/Δh = C(2b)3, where Q is the flow rate, Δh is the difference in hydraulic head, C is a constant that depends on the flow geometry and fluid properties, and 2b is the fracture aperture. The validity of this law for flow in a closed fracture where the surfaces are in contact and the aperture is being decreased under stress has been investigated at room temperature by using homogeneous samples of granite, basalt, and marble. Tension fractures were artificially induced, and the laboratory setup used radial as well as straight flow geometries. Apertures ranged from 250 down to 4µm, which was the minimum size that could be attained under a normal stress of 20 MPa. The cubic law was found to be valid whether the fracture surfaces were held open or were being closed under stress, and the results are not dependent on rock type. Permeability was uniquely defined by fracture aperture and was independent of the stress history used in these investigations. The effects of deviations from the ideal parallel plate concept only cause an apparent reduction in flow and may be incorporated into the cubic law by replacing C by C/ƒ. The factor ƒ varied from 1.04 to 1.65 in these investigations. The model of a fracture that is being closed under normal stress is visualized as being controlled by the strength of the asperities that are in contact. These contact areas are able to withstand significant stresses while maintaining space for fluids to continue to flow as the fracture aperture decreases. The controlling factor is the magnitude of the aperture, and since flow depends on (2b)3, a slight change in aperture evidently can easily dominate any other change in the geometry of the flow field. Thus one does not see any noticeable shift in the correlations of our experimental results in passing from a condition where the fracture surfaces were held open to one where the surfaces were being closed under stress.

/pdf/validity-of-cubic-law-for-fluid-flow-in-a-deformable-rock-2ynq4id3hq.pdf

VALIDITY OF CUBIC LAW FOR FLUID FLOW IN A DEFORMABLE ROCK FRACTURE - eScholarship

Time is divided by geologists according to marked shifts in Earth's state. Recent global environmental changes suggest that Earth may have entered a new human-dominated geological epoch, the Anthropocene. Here we review the historical genesis of the idea and assess anthropogenic signatures in the geological record against the formal requirements for the recognition of a new epoch. The evidence suggests that of the various proposed dates two do appear to conform to the criteria to mark the beginning of the Anthropocene: 1610 and 1964. The formal establishment of an Anthropocene Epoch would mark a fundamental change in the relationship between humans and the Earth system.

Defining the Anthropocene

Solar cells based on organic-inorganic lead halide perovskites are popular in the photovoltaic community due to their high efficiency, low cost, and solution processability. Understanding the fundamentals of metal halide perovskite and its interfaces is extremely important for achieving high-quality materials and developing efficient devices using these materials with the necessary properties. Various methodologies have been used to evaluate the excellent optoelectronic properties, efficiency, and stability of PSCs. In this article, we reviewed the case studies of characterization techniques to investigate structural, optical, and electrical properties of perovskite material via electron microscopic techniques (SEM and TEM), J-V measurements, AFM, XRD, and spectroscopy techniques (PL, UV-vis, XPS, Raman, FTIR, and EIS). PSCs also need to have long-term stability and large-scale applicability for successful commercialization. In this review, we studied perovskite in detail to understand the key properties of the materials to facilitate the commercialization of PSCs.

https://www.lidsen.com/journals/cr/cr-02-04-033/cr.2204033.pdf

Perovskite Solar Cells: Assessment of the Materials, Efficiency, and Stability

The development of society has led to more and more sound sources giving higher and higher noise levels. Dhanbad, one of the polluted city of Bihar, is famous for the prime coking coal. The re are a number of mines and coal – based industrial in this region which have made the region vibrant in terms of noise pollution. It was found that none of the area noise levels were less than 45 dBA. Even in the silence zones noise levels were found to exceed the limit of 55 dBA in the night hours also. In order to evaluate the existing noise levels in Dhanbad municipal area, a study has been conducted and also some control measures has been suggested.

The Status of Noise Pollution in Dhanbad Municipal Area

The information on the soundness of rock is very important for enduring safety and stability of miming, marine and civil structures. The present paper mainly deals with a fuzzy approach to determine the effect of acidic watery environment on the rock strength of the sandstone rock sample. Fuzzy inference system developed here intelligently predicts the competency of the rock, based on experimental data used for the model development. The approach used would be able to predict the relative rock strength at any range of acidic to basic watery environment for any geotechnical investigation or application to achieve long-term durability.

A fuzzy approach to classify physico-mechanical rock property with varying pH of the surrounding medium

The Artificial Neural Network (ANN) has been used as a predictive tool for the estimation of certain parameters of Subernarekha, an important river in the Jharkhand state in India. The network used two algorithms for this purpose and was sufficiently accurate in predicting the most economically heavy and time-consuming set of data. The Levenberg-Marquardt Backpropagation Network (trainlm) and the Resilient Backpropagation Network (trainrp) were the two algorithms used for the estimation of metallic species and physicochemical parameters of the river. The MAPE for metallic species were found to be 0.71 for cadmium, 0.182 for copper and 0.771 for chromium, while physicochemical parameters were 16.645 for alkalinity, 5.883 for dissolved oxygen (DO) and 23.28 for chemical oxygen demand (COD). Both the algorithms were used with different sets of hidden layers i.e., one for trainlm with 5 neurons and three for trainrp with 5, 4 and 5 neurons, and these were determined using the trial and error method. This method is not only economically favorable but time-adaptive as well, as it depends on the amount and span of data available and it can predict values to a very high degree of accuracy. This method can successfully be employed for the prediction of parameters of any river system with confidence.

Prediction of Various Parameters of a River for Assessment of Water Quality by an Intelligent Technique

BARC has been working towards the development of gas bearing supported high speed turboexpander rotors for use in indigenous helium liquefiers and refrigerators. Extensive experiments have been carried out to obtain the dynamic characteristics of the rotor both during coast-up as well as coast-down operations. The objective of these experiments is to identify the critical speeds of the rotor and relate it with the bearing clearance. This would enable design of radial bearings with proper clearance so as to avoid the occurrence of critical speed near the range of rated rotor operational speeds. The present paper documents the experience of stable rotation of several 16 mm diameter cryogenic turboexpander rotors during recent laboratory test runs. Snap shots from FFT analyzer during the experiments as well as synchronous response to unbalance for coast-up and coast-down operations have been included.

Trilok Singh

Papers

Perovskite Solar Cells: Assessment of the Materials, Efficiency, and Stability

The Status of Noise Pollution in Dhanbad Municipal Area

A fuzzy approach to classify physico-mechanical rock property with varying pH of the surrounding medium

Prediction of Various Parameters of a River for Assessment of Water Quality by an Intelligent Technique

High Speed Cryogenic Turboexpander Rotor for stable operation up to 4.5 kHz Rotational Speed