Grading and metastable effects in admittance spectroscopy of CIGS-based solar cells

Cu(In, Ga)Se2-based (CIGS) solar cells have achieved efficiencies up to 20%. Despite these excellent results, the understanding of the underlying mechanisms and the influence of defects on their performance is still incomplete. The determination of the energetic position of the defects and of their density of states is important. Admittance spectroscopy is an adequate technique for this. By varying the external voltage during the measurement, the spatial position where the defect distribution is sensed can be varied. However, the application of external biases can lead to metastable effects in the absorber and therefore to defect relaxation and changes in the doping distribution. Hence, it is important to separate between the effects caused by metastable changes and the change in sensing position of the admittance spectroscopy measurement. This can be achieved by varying the applied voltage during the creation of the metastable state and the measurement itself independently or simultaneously. Admittance spectroscopy under different bias voltage conditions performed on a flexible CIGS-based solar cell are presented and assessed

Assignment of capacitance spectroscopy signals of CIGS solar cells to effects of non-ohmic contacts

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Comparison of Wheel-Rail Contact Modelling in Multibody System Online Simulation

The wheel-rail contact modelling is always an interesting topic in rail vehicle system dynamics simulation. Many contact models have been developed for different purposes, and each model has its own pros and cons for different applications. In multibody system (MBS) simulation of rail vehicles, the efficiency and accuracy of the wheel-rail contact model are of importance. It is the aim of this paper to compare in MBS online simulation one classical approach (Hertz theory+FASTSIM), one approximated non-Hertzian approach and the ‘exact’ solver CONTACT and show the influences of the contact modelling on the results of vehicle dynamics simulations

Combining optical and electrical studies to unravel the effect of Sb doping on CIGS solar cell

A way to lower the manufacturing cost of Cu(In,Ga)Se2 (CIGS) thin film solar cells is to use flexible polymer substrates instead of glass substrates. Because such substrates require a low temperature during absorber deposition, the efficiency of the cells remains slightly lower (18.7%) compared to CIGS on glass substrates (20.3%). Partial compensation of this efficiency loss might be accomplished by Sb doping of the absorber, which is reported to have a positive effect on the morphology of this layer. In this work the defect structure of Sb doped CIGS solar cells is investigated using optical and electrical spectroscopic techniques. Experiments were performed on cells deposited on soda lime glass substrate, adding a thin Sb layer (8, 12 nm) onto the Mo back contact prior to the CIGS absorber deposition. The results are compared with those for cells without Sb doping using the same process. Fourier-Transform near infrared photocurrent measurements in the 10–300K range demonstrate that the band gap of Sb-doped samples is larger than for undoped samples. Photoluminescence spectra in the 5–100K region provide information on shallow-level defects. Deep-Level Transient Spectroscopy spectra of Sb-doped cells exhibit two features not encountered for non-doped cells: 1) a peak at lower temperature than the N1 signal and 2) incomplete charge carrier freeze-out down to 8 K. While the first result appears to be the fingerprint of an extra non-Ohmic contact in the solar cell structure, the second suggests the introduction of a very shallow acceptor by Sb doping. As a salient feature one can accurately monitor the partial hole freeze-out in the 40-60 K range and determine the signature of the intrinsic defects that provide the p-type conductivity of the CIGS absorber using Admittance Spectroscopy

Ambient-aware continuous care through semantic context dissemination

Background: The ultimate ambient-intelligent care room contains numerous sensors and devices to monitor the patient, sense and adjust the environment and support the staff. This sensor-based approach results in a large amount of data, which can be processed by current and future applications, e. g., task management and alerting systems. Today, nurses are responsible for coordinating all these applications and supplied information, which reduces the added value and slows down the adoption rate. The aim of the presented research is the design of a pervasive and scalable framework that is able to optimize continuous care processes by intelligently reasoning on the large amount of heterogeneous care data. Methods: The developed Ontology-based Care Platform (OCarePlatform) consists of modular components that perform a specific reasoning task. Consequently, they can easily be replicated and distributed. Complex reasoning is achieved by combining the results of different components. To ensure that the components only receive information, which is of interest to them at that time, they are able to dynamically generate and register filter rules with a Semantic Communication Bus (SCB). This SCB semantically filters all the heterogeneous care data according to the registered rules by using a continuous care ontology. The SCB can be distributed and a cache can be employed to ensure scalability. Results: A prototype implementation is presented consisting of a new-generation nurse call system supported by a localization and a home automation component. The amount of data that is filtered and the performance of the SCB are evaluated by testing the prototype in a living lab. The delay introduced by processing the filter rules is negligible when 10 or fewer rules are registered. Conclusions: The OCarePlatform allows disseminating relevant care data for the different applications and additionally supports composing complex applications from a set of smaller independent components. This way, the platform significantly reduces the amount of information that needs to be processed by the nurses. The delay resulting from processing the filter rules is linear in the amount of rules. Distributed deployment of the SCB and using a cache allows further improvement of these performance results

Corporate Entrepreneurship:From Structures to Mindset

Corporate entrepreneurship dispersed throughout an organization and leveraging the entrepreneurial potential of all its employees bears significant benefits for those organizations that embrace it. However, it appears more difficult to instill and requires strong investment in the development of human capital and entrepreneurial mindset among the employees and across the organization. In this chapter, we discuss the essence of corporate entrepreneurship mindset and show that across an organization, there might be different entrepreneurial mindsets that correspond to different people, opportunities, and contexts. Although different, they all lead to enactment of entrepreneurial projects. This chapter, thus, contributes to the discussion regarding the nature of corporate entrepreneurial mindsets, and their development and stimulation within an organization, from both academic and practical view

Optical pump rectification emission: route to terahertz free-standing surface potential diagnostics

We introduce a method for diagnosing the electric surface potential of a semiconductor based on THz surface generation. In our scheme, that we name Optical Pump Rectification Emission, a THz field is generated directly on the surface via surface optical rectification of an ultrashort pulse after which the DC surface potential is screened with a second optical pump pulse. As the THz generation directly relates to the surface potential arising from the surface states, we can then observe the temporal dynamics of the static surface field induced by the screening effect of the photo-carriers. Such an approach is potentially insensitive to bulk carrier dynamics and does not require special illumination geometries

Group support systems features and their contribution to technology strategy decision-making: A review and analysis

Collective decision-making processes require careful design considerations in organizations. On one hand, the inclusion of a greater number of actors contribute to a wider knowledge base, on the other, it can become a diffuse process and be distorted from the principles initially established. This paper observes a specific collective decision making process in organizations—technology strategy formulation—and, through a critical review of the literature, analyzes how the advances in features of group support systems support improvements in different stages of this process. This paper also discusses the implications of GSS appropriation in group dynamics.This research was supported by Fundação para a Ciência e Tecnologia (SFRH/ BD/ 33727/ 2009), within the framework of the MIT Portugal Program.info:eu-repo/semantics/publishedVersio

Entrepreneurial orientation and the business performance of SMEs: a quantitative study from the Netherlands

Entrepreneurial Orientation (EO) is often mentioned as an antecedent of growth, competitive advantage and superior performance, and prior empirical research has often shown a positive relationship between EO and performance appears to exist. However, an important question that remains unanswered is what effect EO might have on firm performance during periods of economic crisis, and the severe environmental turbulence that accompany such crises. This research is a first investigation towards the effects of EO on the performance of small and medium sized firms during the current global economic crisis. In this study we use the multidimensional model of EO and test a series of hypotheses pertaining to its performance effects using survey data gathered from 164 Dutch SMEs. The present research shows that proactive firm behavior positively contributes to SME performance during the economic crisis. We further show that innovative SMEs do perform better in turbulent environments, but those innovative SMEs should minimize the level of risk and should take action to avoid projects that are too risky