Petr Sládek

Improvement of the efficiency of the silicon solar cells by silicon incorporated diamond-like carbon antireflective coatings

Silicon incorporated diamond-like antireflective coatings were deposited upon the silicon solar cells in order to improve their efficiency. The films were prepared by plasma enhanced chemical vapor deposition (PECVD) technique from the mixture of hexamethyldisiloxane (HMDSO) and methane. The optical and tribological properties of the coatings could be easily changed by the percentage of the HMDSO in the deposition feed.

Metastability of Phosphorus or Boron doped a-Si:H films

The effects of light-soaking on either phosphorus- or boron-doped a-Si:H films were studied as functions of the doping level and the temperature. In the case of boron-doped films, the most important effect is the improvement of the conductivity during light-soaking, which is related to the activation of boron. On the contrary, phosphorus-doped films present a remarkable stability, although lightly phosphorus-doped ones show a decrease of their conductivity by five orders of magnitude when light-soaking is performed below 40 °C. This effect is attributed to the formation of P-H complexes which are stable at low temperature only. Our results suggest that in both types of doped a-Si:H films the creation of metastable defects is a second order effect with respect to the activation or passivation of dopants, which results from their interaction with hydrogen.

Defect states in the intrinsic layer of amorphous silicon solar cells studied by the constant-photocurrent method

Abstract The constant-photocurrent method (CPM), which has been widely used for the study of the defect density in the gap of hydrogenated amorphous silicon (a-Si: H) films, is applied to study the defect density in the intrinsic layer of a-Si: H-based solar cells. The analysis of the CPM-derived absorption spectrum in p-i-n devices indicates that reliable measurements can be performed under short-circuit or reverse-bias conditions. In these conditions the CPM measurement is limited by the transport of holes and therefore is a good indicator of the quality of the intrinsic layer. Moreover, we show that CPM is sensitive to that part of the i layer in which the Fermi level is around midgap. Comparison of CPM spectra in films and cells is used to determine the conditions under which the measurements in the solar cell are relative to the properties of the intrinsic layer or sensitive to interface effects. Deconvolution of the CPM spectrum according to a standard model of the defect density distribution in a-S...

Analysis of the temperature dependence of the CPM-derived optical absorption spectra of hydrogenated amorphous silicon films

Abstract The observed modifications with temperature (from 300 to 77K) of carefully calibrated CPM-derived optical absorption spectra, especially in the low-energy range (hv

Properties of atmospheric pressure plasma oxidized layers on silicon wafers

Abstract In this research a new process of plasma oxidation of crystalline silicon at room temperature is studied. The plasma oxidation was carried out using Diffuse Coplanar Surface Barrier Discharge (DCSBD) operating in ambient air and oxygen at atmospheric pressure. The influence of exposition time, plasma parameters and crystallographic orientation of silicon on oxidized layers and their dielectric properties were investigated. Thickness, structure and morphology of these layers were studied by ellipsometry, infrared absorption spectroscopy and scanning electron microscopy. During the treatment time, from 1 to 30 minutes, oxidized layers were obtained with thickness from 1 to 10 nm. Their roughness depends on the crystallographic orientation of silicon surface and exposure time. Electrical parameters of the prepared layers indicate the presence of an intermediate layer between silicon substrate and the oxidized layer. Graphical Abstract

Remote laboratories - multiple task server

Remote laboratories, i.e., laboratory accessed via the PC and the Internet, represent one of the unusual opportunities of todays applications of Internet and computer technology. Moreover, the rapid development of the computerized “remote” activities in daily life requires training of the appropriate skills. The goal of remote laboratories is not to replace the classic experiment, but to provide an existing physical experiment to someone who has no, for whatever reason, the possibility of making a classic experiment in his own laboratory. The important thing is that remote laboratory enable access to real experiments and does not represent simulation, or modeled physical phenomenon, or recording. In our paper we present new possibility of the interface between several classic experiments and one server created based on system ISES and software for remote laboratory ISES Web Control.

The hydrogen effusion induced structural changes and defects in hydrogenated amorphous SiGe films: dependence upon the microstructure

Abstract To better understand the relations between deposition conditions, microstructure, H incorporation and the optoelectronics properties of undoped a-Si1−x Gex:H alloys, we performed a comparative study of samples (with x≈0.5) prepared by plasma enhanced chemical vapour deposition at total pressures varying from 900 to 2200 mTorr. The hydrogen bonding, detected by infra-red absorption measurements and H thermal desorption experiments, as well as the optoelectronic properties, determined by a combination of standard optical and photothermal deflection spectroscopy measurements, were found to depend on the total pressure. The results obtained in the as-deposited state and after annealing at increasing temperatures are analysed as a whole in terms of specific local H bonding environment, degree of order, and defects.

Experimental aspects of the constant photocurrent method applied to a-Si: H

Abstract The so-called constant photocurrent method is widely used for the study of the density of states in the gap of hydrogenated amorphous silicon (a-Si: H) and related materials. After recalling the basic principles of the method and the underlying assumptions, we discuss several experimental aspects of its application and propose solutions that allow accurate and reliable optical absorption coefficient spectra to be obtained for a-Si: H over a large energy/absorption range.

Physics Education in Historical Perspective and Future Trends

This article deals with physics education form its emergence in 19th century to the present and outlines future trends. Physics had become part of general education and remains an important part of science literacy. Current breakthrough of information and communication technology (ICT) is based on physics achievements, on the contrary interest of students in science and technology studies has been falling. The traditional role of schools as the main source of information has been replaced by ICT’s and teacher’s role in a modern school has been changing too. ICT’s provide an opportunity for innovation of education methods but they easily distract attention of students from physics content. We discuss physics educational content and teaching methods for different school levels, whether they are appropriate for 21st century education and societal needs. We researched the state and perspectives of physics eduacation in the Czech Republic and identified the problem that number of pre-service teachers do not match the demand of schools for qualified physics teachers. The DOI number of the abstract on the conference pages is: http://dx.d oi.org/1 0.21125/edulearn.2017.2285

THE ROLE OF THE SELF-REFLECTION IN THE UNDERGRADUATE TEACHING PRACTICE IN VOCATIONAL SUBJECTS

The paper discusses about the preparation of the future teachers of the vocational subjects and the vocational training at secondary vocational schools. The research survey is focused on the students of Faculty of Education, Masaryk University in Brno, Czech Republic. The teaching practice in the undergraduate study program represents its integral part. The acquired educational and professional experience is a best way how the future teachers can learn to apply their theoretical knowledge and pedagogical skills in the real work with students. The practice has two parts: Observation of a lesson taught by an experienced teacher and the lesson taught by a student himself. From our survey we believe that a great advantage bring the follow-up seminar after completing the practice in which students discuss their experiences from the implemented practice at school. Interesting are the personal opinions of the students on the organisation of the lesson taught by an experienced teacher at the secondary vocational school. The essential part of this seminar is a self-reflection of each student. The goal of the self-reflection is that students are able to critically evaluate the lesson taught by themselves. We present some benefits from this approach.