Cover - Journal of Achievements in Materials and Manufacturing

Cover - Journal of Achievements in Materials and Manufacturing

ISSN 1734-8412
Editor-in-Chief Prof. Leszek A. Dobrzański
http://www.journalamme.org
Volume 29 • Issue 1 • July 2008
PUBLISHED SINCE 1992
formerly as Proceedings on
of Achievements in Materials
and Manufacturing Engineering
Achievements in Mechanical
and Materials Engineering
Published monthly as the organ of the World Academy of Materials and Manufacturing Engineering
Editor-in-Chief
Editorial Board
Prof. Leszek A. Dobrzaƒski - Gliwice, Poland
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Deputies Editor-in-Chief
South America
Prof. Maria Helena Robert - Campinas, Brazil
North America
Prof. George Totten - Portland, USA
Europe
Prof. Jose Manuel Torralba - Madrid, Spain
Asia
Prof. Yong Taek Im - Daejeon, South Korea
Australia
Prof. Kanaka Durga Vara Prasad Yarlagadda
- Brisbane, Australia
Africa
Prof. Abdalla Wifi - Cairo, Egypt
Associate Editors
Dr Mirosław Bonek
Dr Małgorzata Drak
Dr Klaudiusz Gołombek
Ms Marzena Kraszewska, MA
Dr Janusz Madejski
Dr Daniel Pakuła
Editorial Assistance
Dr Magdalena Polok-Rubiniec
Dr Anna Włodarczyk-Fligier
Dr Bogusław Zi´bowicz
Ms Barbara Doł˝aƒska, MSc
Ms Justyna Hajduczek, MSc
Reading Direct
Dr Adam Polok
Mr Piotr Zarychta, MSc
Reading Direct
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Gilmar Batalha - Sao Paulo, Brazil
Emin Bayraktar - St-Ouen, France
Milan Brandt - Swinburne, Australia
Tara Chandra - Wollongong, Australia
Antonio Cuhna - Guimaraes, Portugal
Marek Dollar - Oxford, Ohio, USA
J. Paulo Davim - Aveiro, Portugal
Sabahudin Ekinoviç - Zenica, Bosnia and Herzegovina
Renato Esposito - Naples, Italy
Spilios Fassois - Patras, Greece
Swadhin Ghosh - Rösrath, Germany
Janez Grum - Ljubljana, Slovenia
Toshio Haga - Osaka, Japan
Abdel Magid Hamouda - Doha, Qatar
Stuart Hampshire - Limerick, Ireland
Lauri Holappa - Espoo, Finland
John Barry Hull - Nottingham, United Kingdom
Mark James Jackson - West Lafayette, Indiana, USA
Krzysztof Jemielniak - Warsaw, Poland
Jerzy J´drzejewski - Wroc∏aw, Poland
Yosef Katz - Beer Sheva, Israel
Andrzej Klimpel - Gliwice, Poland
Ivars Knets - Riga, Latvia
Janez Kopac - Ljubljana, Slovenia
Karl Kuzman - Ljubljana, Slovenia
Anatolij Kuzmenko - Khmielnitsky, Ukraine
Petr Louda - Liberec, Czech Republic
Stanis∏aw Mitura - ¸ódê, Poland
Andrew Nee - Singapore, Singapore
Jerzy Nowacki - Szczecin, Poland
Abraham Ogwu - Paisley, United Kingdom
Fusheng Pan - Chongqing, China
Mario Rosso - Turin, Italy
Antonio Sousa - Fredericton, NB, Canada
Božo Smoljan - Rijeka, Croatia
Jerry Sokolowski - Windsor, Ontario, Canada
Zinovij Stotsko - Lviv, Ukraine
Jerzy Âwider - Gliwice, Poland
Ming-Jen Tan - Singapore, Singapore
Boris Tomov - Rousse, Bulgaria
Marcel Van De Voorde - Brussels, Belgium
Senay Yalcin - Istambul, Turkey
Bekir Sam Yilbas - Dhahran, Saudi Arabia
of Achievements in Materials
and Manufacturing Engineering
Patronage
Cover story
Silicon is the main
material on which phodeveloptovoltaics
depends.
It
ment
belongs to n-type
donor semiconductors
or p-type accpetor
ones, depending on its
Editor-in-Chief Prof. Leszek A. Dobrzański
Volume 29 • Issue 1 • July 2008
admixtures. The pentavalent donor elements atoms introduced into silicon (but
also into germanium),
e.g., P or As, or with a
bigger number of palence electrons, bond
with Si (or Ge) atoms
with four electrons
only, introducing the
remaining excess electrons to the semiconductor
conduction
band, demonstrating
the elektron conduction. The conduction
electrons move under
the influence of the
applied electric field
causing charge transfer, and releasing of
http://www.journalamme.org
electrons is favoured
by temperature increase, Chile conductivity gets bigger along with the doping agents atoms concentration increase. Atoms of the trivalent acceptor elements, e.g., B or Al, or with a
smaller number of valence electrons introduce the unfilled energy state called holes
to the valence band, so the electrons from this band are excited to the acceptor
state with energy higher than the upper palence band limit. The hole conduction
grows also with the increase of temperature and concentration of the dope atoms.
The photovoltaic effect occurring in silicon and in some other semiconductors consists in generating a pair of current charge carriers electron-hole in the semiconductor by the solar radiation photons with the energy exceeding the gap of energy
levels of this semiconductor. The electric charge developed this way may undergo
recombination due to which solar energy is converted into heat energy which should
be counteracted. The value of the photovoltaic current depends, among others, on
the power of the solar radiation fetching at Earth, area of the illuminated surface,
and also on the type of material in which the radiation energy absorption takes place.
The intensive research on mastering the photovoltaic cells technology have brought
their efficiency to more than 20%. Photons of the electromagnetic radiation falling
onto the semiconductor surface can be absorbed by it, participating in the photovoltaic effect when the remaining two phenomena of reflecting the photons from the
surface or their transition through the material are useless from the photovoltaics
point of view. If the photon energy is significantly higher than the semiconductor
energy gap width then energy of this surplus is converted into heat energy and is
dissipated. Because of the energy gap specific for silicon about 44% of the solar
radiation energy fetched up can be used. Materials with a bigger energy gap generate a higher photoelectrical voltage; whereas, materials with a smaller energy gap
use bigger part of the solar spectrum and provide a higher short-circuit current.
Silicon is characteristic of a skew energy gap; therefore, photons participate in electron transition from the valence band to the conduction band and one or more
phonons is absorbed or emitted. In semiconductors with such gap the life of carriers is longer than in case of those which have the straight energy gap.
In USA photovoltaic arrays have been used to day mainly on a small scale, for the
light roadside signs or as rooftop panels to provide energy for homes or commercial
buildings. An example are the solar panels on the buildings in the research giant
Google campus, which are expected to provide around 1,600 kW/h of the electricity. The bird’s-eye view of this campus is shown in the first small photo on this Issue
cover.
However, the photovoltaic power stations develop very intensively in the last years
– also in USA. The largest solar power plant in North America was opened in
December 2007, shown in the big photo on this Issue cover. This power station provides electricity to Nellis Air Force Base in the Nevada desert in USA. Nellis, which
is outside Las Vegas, is devoting ca. 56 ha to a massive photovoltaic array with panels of silicon wafers that rotate to follow the sun across the sky and generate electricity. The plant is capable totally of producing 15 MW of the electricity, enough to
provide 30% of the electric needs on the Nellis Air Force Base, where 12,000 people work and 7,215 people live. The Air Force expects to save $1 million a year in
lower electric bills and to use the plant to demonstrate it is boldly advancing the use
of renewable energy technology.
ISSN 1734-8412
World Academy of Materials
and Manufacturing Engineering
Polish Academy of Sciences,
Committee of Materials Science,
Section of Metallic Materials
International Federation of Heat Treatment
and Surface Engineering
Association of Computational Materials
Science and Surface Engineering
Institute of Engineering Materials
and Biomaterials of Silesian University
of Technology, Gliwice, Poland
Financial support
In 2008 the publication of the Journal is financially supported by
the Ministry of Science and Higher Education in Poland.
Abstracting services
This Journal is sent to individual receivers from ca. 50 countries
of the world and is delivered to the National Libraries and
Universities and also to other scientific institutions in ca. 50
countries of the world. The electronic system of Reading Direct
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in the promotional period free of charge. This Journal is included
in the reference list of the Polish Ministry of Science and Higher
Education (6 points). The procedure leading to the citation of
that journal by Abstracting Services has already begun.
Journal Registration
The Journal is registered by the Civil Department of the District
Court in Gliwice, Poland at number 279
Publisher
Gliwice 44-100, Poland
ul. S. Konarskiego 18a/366
e-mail: [email protected]
Bank account:
Stowarzyszenie Komputerowej Nauki o Materia∏ach i In˝ynierii Powierzchni
Bank name: ING Bank Âlàski
Bank address: ul. Zwyci´stwa 28, 44-100 Gliwice, Poland
Account number/ IBAN CODE: PL76105012981000002300809767
Swift code: INGBPLPW
Gliwice – Campinas – Portland – Madrid – Daejeon – Brisbane – Cairo
® 2008 International OCSCO World Press. All rights reserved
The paper used for this Journal meets the requirements of acid-free paper
Printed in Poland
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