Synthesis and characterization of 15% efficient CIGSSe solar cells from nanoparticle inks

We report a total‐area power conversion efficiency of 15% for a copper indium gallium disulfoselenide (CIGSSe) solar cell fabricated from a copper indium gallium disulfide (CIGS) nanoparticle ink based process. Careful optimization of the fabrication process has resulted in a significant improvement in efficiency compared to our previously reported efficiency of 12%. This efficiency ranks among the highest reported in the literature for solution processed CIGSSe. Despite having an absorber thickness of approximately 700–800 nm, which is less than half the thickness of high efficiency devices grown by both coevaporation and solution processes in the literature, our devices show good short‐circuit current (32.1 mA/cm²). Surprisingly, the sintered film shows lateral composition fluctuations, which have not been reported for other high efficiency devices and may be responsible for the lower open circuit voltage (636 mV) observed here. This suggests an avenue for further improvement through optimization of the nanoparticle selenization process to better control composition in the sintered film. Copyright © 2015 John Wiley & Sons, Ltd.     

Phase development and pore stability of yttria- and ytterbia-stabilized zirconia aerogels

High-porosity yttria- and ytterbia-stabilized zirconia aerogels offer the potential of extremely low thermal conductivity materials for high-temperature applications. Yttria- and ytterbia-doped zirconia aerogels were synthesized using a sol-gel approach over the dopant range of 0-20 atomic percent. Surface area, pore volume, and morphology of the as-dried aerogels and materials thermally exposed for short periods of time to temperatures up to 1200°C were characterized by nitrogen physisorption, scanning and transmission electron microscopy, and X-ray diffraction. The aerogels as supercritically dried all were X-ray amorphous. At a 5% dopant level, a tetragonal structure with a smaller monoclinic phase developed on thermal exposure. Mixed tetragonal and cubic phases or predominantly cubic materials were observed at higher dopant levels, depending on the dopant level, temperature and exposure time. The formation of crystalline phases was accompanied by loss of surface area and pore volume, although some mesoporous structure was maintained on short-term exposure to 1000°C. Incorporation of the smaller Yb atom into the lattice structure resulted in smaller lattice dimensions on crystallization than was seen with Y doping and favored a more highly equiaxed structure. Aerogels synthesized with 15% Y maintained the smallest particle size without evidence of sintering at 1100°C. Largest shrinkage and loss of pore volume occurred on crystallization from the amorphous phase, with further loss of pores at temperatures above 1000°C attributable to changes in lattice parameters.     

Energy-efficient cooking methods

Energy-efficient new cooking techniques have been developed in this research. Using a stove with 649?±?20 W of power, the minimum heat, specific heat of transformation, and on-stove time required to completely cook 1 kg of dry beans (with water and other ingredients) and 1 kg of raw potato are found to be: 710 (±24)?kJ, 613 (±20)?kJ, and 1,144?±?10 s, respectively, for beans and 287?±?12 kJ, 200?±?9 kJ, and 466?±?10 s for Irish potato. Extensive researches show that these figures are, to date, the lowest amount of heat ever used to cook beans and potato and less than half the energy used in conventional cooking with a pressure cooker. The efficiency of the stove was estimated to be 52.5?±?2 %. Discussion is made to further improve the efficiency in cooking with normal stove and solar cooker and to save food nutrients further. Our method of cooking when applied globally is expected to contribute to the clean development management (CDM) potential. The approximate values of the minimum and maximum CDM potentials are estimated to be 7.5?×?10¹¹ and 2.2?×?10¹³?kg of carbon credit annually. The precise estimation CDM potential of our cooking method will be reported later.     

An information-processing model of the decision to seek professional help.

Despite the presence of quality mental health care in many communities, people tend to avoid seeking help and wind up languishing in their problems unnecessarily. For the professional to better understand how to reach these individuals, an information-processing model is presented that examines the effects of people's interpretation of their environment and their symptoms on their decision to seek mental health services. Using the model as a guide, suggestions are presented for practitioners who wish to provide services to those who are in need of professional help, yet are hesitant to obtain it. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Calculation of performance of fire retardant ceiling systems

With equations, Part I describes the thermal behavior of a composite system consisting of a noncombustible ceiling board suspended below a concrete floor slab. Part II shows how the equations have been successfully adapted to digital computer operation. The computed results agree with experimental measurements for two specific systems exposed to a standard test furnace heated at a prescribed rate. Note: References 1 through 11, Table 1, and Figures 1 and 2 will be found in Part I of this paper published inFire Technology, Vol. 5, No. 4, November 1969, on pages 323–331.     

Program verification with interacting analysis plugins

In this paper we propose and argue for a modular framework for interprocedural program analysis, where multiple program analysis tools are combined in order to exploit the particular advantages of each. This allows for “plugging together” such tools as required by each verification task and makes it easy to integrate new analyses. Our framework automates the sharing of information between plugins using a first order logic with transitive closure, in a way inspired by the open product of Cortesi et al. We describe a prototype implementation of our framework, which performs static assertion checking on a simple language for heap-manipulating programs. This implementation includes plugins for three existing approaches—predicate abstraction, 3-valued shape analysis and a decidable pointer analysis—and for a simple type system. We demonstrate through a detailed example the increase in precision that our approach can provide. Finally we discuss the design decisions we have taken, in particular the tradeoffs involved in the choice of language by which the plugins communicate, and identify some future directions for our work. R. Lazic, R. Nagarajan and J. C. P. Woodcock     

Real-time dynamic optimization of batch systems

In this paper a methodology for designing and implementing a real-time optimizing controller for batch processes is proposed. The controller is used to optimize a user-defined cost function subject to a parameterization of the input trajectories, a nominal model of the process and general state and input constraints. An interior point method with penalty function is used to incorporate constraints into a modified cost functional, and a Lyapunov based extremum seeking approach is used to compute the trajectory parameters. The technique is applicable to general nonlinear systems. A precise statement of the numerical implementation of the optimization routine is provided. It is shown how one can take into account the effect of sampling and discretization of the parameter update law in practical situations. A simulation example demonstrates the applicability of the technique.     

Determination of Thermophysical Properties for Polymer Films using Conduction Analysis of Laser Heating

Determination of the thermophysical properties of thin film materials is important for modeling and optimizing laser microvia drilling of organic substrates in microelectronics applications. Techniques to measure the density, thermal conductivity, thermal diffusivity, thermal decomposition point, and specific ablation heat of thin polymer films are described. An experimental apparatus was set up for laser heating of the sample. To measure the thermal diffusivity, an analytic heat transfer model is developed. One-dimensional heat conduction is assumed due to the small thickness of the film compared to the radius of the laser beam. The value of thermal diffusivity is obtained by fitting the experimental data to the theory. The specific ablation heat is obtained by measuring the mass loss during laser ablation. The experimental apparatus and the property determination methodology can also be applied to thin samples of other materials.     

The Concept of Planned Development: A Presentation and Commentaries on the Contribution of Nathaniel Lichfield

This article and the commentaries which accompany it centres on a reflection by consultant-academic Nathaniel Lichfield on his work on planned development and the evaluation of the impacts of such development, over a career spanning the past 60 years. His work, in the UK and across the world, had a formative influence on generations of planners brought up on his texts. In this presentation, David Adams sets the context of his contribution. The heart of the article is a reflective synthesis by Lichfield on his own work from his first major contribution in 1956, to its evolution in the 1960s into the technique of the Planning Balance Sheet, and later, Community Impact Evaluation. His starting point is that there can be urban and regional planning which does not lead to physical development on the ground and there can be such development on the ground that has not been influenced by government led urban and regional planning. Neither of these is planned development. This takes place when the two are fused together in practice: the development and the government led planning. It is this simple concept, with particular emphasis on its economics, which was treated at length in the Economics of Planned Development (1956). In order to fully describe the concept, the book's contents are summarized in the first half of this article following an introduction of the background. Following the publication of the book, Lichfield's professional and academic work took him in many directions, much of which fell loosely under the ambit of the economics of planned development. His contributions were not written up as sequels to the book but rather in related books, papers and articles under an array of topics. He terms these 'the children of EPD'. They are described in the second half of the article, grouped in relation, as appropriate, to each of the main themes of the 1956 book and extensions of it. Lichfield's article is followed by three commentaries. The first, by Mike Teitz, positions his work and its later development in the changing context of the times. The second, by Barrie Needham, provides some critical thoughts on how well the concept of 'planned development' travels transnationally into different institutional contexts. The third, from consultant-planner Alan Wenban-Smith, himself working on policy evaluation in the UK, explores the practical and methodological robustness of Lichfield's concepts. Overall, the piece provides an input to reflections on the relation between state and market in the development process and on the evaluative stance the state should take to its interventions.