Free ebooks ==> www.Ebook777.com www.Ebook777.com Free ebooks ==> www.Ebook777.com IFIP Advances in Information and Communication Technology 349 Editor-in-Chief A Joe Turner, Seneca, SC, USA Editorial Board Foundations of Computer Science Mike Hinchey, Lero, Limerick, Ireland Software: Theory and Practice Bertrand Meyer, ETH Zurich, Switzerland Education Arthur Tatnall, Victoria University, Melbourne, Australia Information Technology Applications Ronald Waxman, EDA Standards Consulting, Beachwood, OH, USA Communication Systems Guy Leduc, Université de Liège, Belgium System Modeling and Optimization Jacques Henry, Université de Bordeaux, France Information Systems Jan Pries-Heje, Roskilde University, Denmark Relationship between Computers and Society Jackie Phahlamohlaka, CSIR, Pretoria, South Africa Computer Systems Technology Paolo Prinetto, Politecnico di Torino, Italy Security and Privacy Protection in Information Processing Systems Kai Rannenberg, Goethe University Frankfurt, Germany Artificial Intelligence Tharam Dillon, Curtin University, Bentley, Australia Human-Computer Interaction Annelise Mark Pejtersen, Center of Cognitive Systems Engineering, Denmark Entertainment Computing Ryohei Nakatsu, National University of Singapore www.Ebook777.com IFIP – The International Federation for Information Processing IFIP was founded in 1960 under the auspices of UNESCO, following the First World Computer Congress held in Paris the previous year An umbrella organization for societies working in information processing, IFIP’s aim is two-fold: to support information processing within its member countries and to encourage technology transfer to developing nations As its mission statement clearly states, IFIP’s mission is to be the leading, truly international, apolitical organization which encourages and assists in the development, exploitation and application of information technology for the benefit of all people IFIP is a non-profitmaking organization, run almost solely by 2500 volunteers It operates through a number of technical committees, which organize events and publications IFIP’s events range from an international congress to local seminars, but the most important are: • The IFIP World Computer Congress, held every second year; • Open conferences; • Working conferences The flagship event is the IFIP World Computer Congress, at which both invited and contributed papers are presented Contributed papers are rigorously refereed and the rejection rate is high As with the Congress, participation in the open conferences is open to all and papers may be invited or submitted Again, submitted papers are stringently refereed The working conferences are structured differently They are usually run by a working group and attendance is small and by invitation only Their purpose is to create an atmosphere conducive to innovation and development Refereeing is less rigorous and papers are subjected to extensive group discussion Publications arising from IFIP events vary The papers presented at the IFIP World Computer Congress and at open conferences are published as conference proceedings, while the results of the working conferences are often published as collections of selected and edited papers Any national society whose primary activity is in information may apply to become a full member of IFIP, although full membership is restricted to one society per country Full members are entitled to vote at the annual General Assembly, National societies preferring a less committed involvement may apply for associate or corresponding membership Associate members enjoy the same benefits as full members, but without voting rights Corresponding members are not represented in IFIP bodies Affiliated membership is open to non-national societies, and individual and honorary membership schemes are also offered Luis M Camarinha-Matos (Ed.) Technological Innovation for Sustainability Second IFIP WG 5.5/SOCOLNET Doctoral Conference on Computing, Electrical and Industrial Systems, DoCEIS 2011 Costa de Caparica, Portugal, February 21-23, 2011 Proceedings 13 Free ebooks ==> www.Ebook777.com Volume Editor Luis M Camarinha-Matos New University of Lisbon Faculty of Sciences and Technology Campus de Caparica, 2829-516 Monte Caparica, Portugal E-mail: cam@uninova.pt ISSN 1868-4238 e-ISSN 1868-422X e-ISBN 978-3-642-19170-1 ISBN 978-3-642-19169-5 DOI 10.1007/978-3-642-19170-1 Springer Heidelberg Dordrecht London New York Library of Congress Control Number: 2011920513 CR Subject Classification (1998): C.2, H.1, C.4, I.2.9, C.3, J.2 © International Federation for Information Processing 2011 This work is subject to copyright All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, re-use of illustrations, recitation, broadcasting, reproduction on microfilms or in any other way, and storage in data banks Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer Violations are liable to prosecution under the German Copyright Law The use of general descriptive names, registered names, trademarks, etc in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use Typesetting: Camera-ready by author, data conversion by Scientific Publishing Services, Chennai, India Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com) www.Ebook777.com Preface Technological Innovation and Sustainability Concerns The subject of sustainability is a concern of growing importance, present in most strategic and political agendas, and also a prevalent issue in science and technology, leading to related terms such as sustainable development and even sustainability science Encompassing a growing awareness of the political sectors and society in general for the importance of sustainability, the business sector has also started to acknowledge that preserving the environment and the other inter-related pillars of sustainability, i.e., the economic and social dimensions, is both good business and a moral obligation New technological developments, in all fields, as major drivers of change, need to embed such concerns as well As doctoral programs in science and engineering are important sources of innovative ideas and techniques that might lead to new products, technological innovation, and even new organizational and governance models with strong economic impact, it is important that the issue of sustainability becomes an intrinsic part of those programs Typically, PhD students are not experienced researchers, being rather in the process of learning how to research Nevertheless, a number of empiric studies also show that a high number of technological innovation ideas are produced in the early careers of researchers From the combination of the eagerness to try new approaches and directions of young doctoral students with the experience and broad knowledge of their supervisors, an important pool of innovation potential emerges The DoCEIS series of doctoral conferences on Computing, Electrical and Industrial Systems aim at creating a space for sharing and discussing ideas and results from doctoral research in these inter-related areas of engineering Innovative ideas and hypotheses can be better enhanced when presented and discussed in an encouraging and open environment DoCEIS aims to provide such an environment, releasing PhD students from the pressure of presenting their propositions in more formal contexts The second edition of DoCEIS, which was sponsored by SOCOLNET, IFIP and the IEEE Industrial Electronics Society, attracted a considerable number of paper submissions from a large number of PhD students (and their supervisors) from 16 countries This book comprises the works selected by the International Program Committee for inclusion in the main program and covers a wide spectrum of topics, ranging from collaborative enterprise networks to microelectronics Thus, novel results and ongoing research are presented, illustrated, and discussed in areas such as: – Collaborative networks models and support – Service-oriented systems – Computational intelligence VI – – – – – – Preface Robotic systems Petri nets Fault-tolerant systems Systems modelling and control Sensorial perception and signal processing Energy systems and novel electrical machinery As a gluing element, all authors were asked to explicitly indicate the (potential) contribution of their work to sustainability We expect that this book will provide readers with an inspiring set of promising ideas, presented in a multi-disciplinary context, and that by their diversity these results can trigger and motivate new research and development directions We would like to thank all the authors for their contributions We also appreciate the dedication of the DoCEIS Program Committee members who both helped with the selection of articles and contributed with valuable comments to improve their quality December 2010 Luis M Camarinha-Matos Second IFIP / SOCOLNET Doctoral Conference on COMPUTING, ELECTRICAL AND INDUSTRIAL SYSTEMS Costa de Caparica, Portugal, February 21 _ 23, 2011 Conference and Program Chair Luis M Camarinha-Matos (Portugal) Program Committee Hamideh Afsarmanesh (The Netherlands) Jose Aguado (Spain) Amir Assadi (USA) Jos´e Barata (Portugal) Arnaldo Batista (Portugal) Luis Bernardo (Portugal) Xavier Boucher (France) Erik Bruun (Denmark) Giuseppe Buja (Italy) Ant´ onio Cardoso (Portugal) Jo˜ao Catal˜ ao (Portugal) Wojciech Cellary (Poland) Jean-Jacques Chaillout (France) David Chen (France) Fernando J Coito (Portugal) Ilhami Colak (Turkey) Luis Correia (Portugal) Carlos Couto (Portugal) Jos´e Craveirinha (Portugal) Jorge Dias (Portugal) H Bulent Ertan (Turkey) Ip-Shing Fan (UK) Florin G Filip (Romania) Tarek Hassan (UK) Maria Helena Fino (Portugal) Jos´e M Fonseca (Portugal) Jo˜ao Goes (Portugal) Luis Gomes (Portugal) Antoni Grau (Spain) Jose Luis Huertas (Spain) Emmanouel Karapidakis (Greece) Stephan Kassel (Germany) Bernhard Katzy (Germany) Marian Kazmierkowki (Poland) Tomasz Janowski (Macau) Ricardo Jardim-Gon¸calves (Portugal) Pontus Johnson (Sweden) Paulo Leit˜ ao (Portugal) J Tenreiro Machado (Portugal) Jo˜ao Martins (Portugal) Maria Carmo Medeiros (Portugal) Paulo Miyagi (Brazil) Jă org Mă uller (Germany) Horacio Neto (Portugal) Rui Neves-Silva (Portugal) Mauro Onori (Sweden) Manuel D Ortigueira (Portugal) Angel Ortiz (Spain) Luis Palma (Portugal) Willy Picard (Poland) Paulo Pinto (Portugal) Ricardo Rabelo (Brazil) Hubert Razik (France) Sven-Volker Rehm (Germany) Rita Ribeiro (Portugal) Juan Jose Rodriguez (Spain) Enrique Romero (Spain) Jos´e de la Rosa (Spain) Luis S´ a (Portugal) Gheorghe Scutaru (Romania) Fernando Silva (Portugal) Adolfo Steiger Gar¸c˜ao (Portugal) Klaus-Dieter Thoben (Germany) VIII Organization Stanimir Valtchev (Portugal) Manuela Vieira (Portugal) Christian Vogel (Austria) Antonio Volpentesta (Italy) Organizing Committee Co-chairs Luis Gomes (Portugal), Jo˜ao Goes (Portugal), Jo˜ ao Martins (Portugal) Organizing Committee (PhD Students) Jos´e Lima Carla Gomes Elena Baikova Francisco Ganh˜ ao Miguel Carneiro Vitor Fialho Arnaldo Gouveia Dora Gon¸calves Edinei Santin Jo˜ ao Casaleiro Manuel Vieira Ant´ onio Pombo Eduardo Pinto Fernando Pereira Filipe Moutinho Jos´e Lucas Raul Cordeiro Svetlana Chemetova Eduardo Eus´ebio Joao Costa Jos´e Luzio Jos´e Silva Nuno Cardoso Technical Sponsors SoCol net Society of Collaborative Networks IFIP WG 5.5 COVE Co-Operation infrastructure for Virtual Enterprises and electronic business IEEE−Industrial Electronics Society Free ebooks ==> www.Ebook777.com Organization IX Organizational Sponsors UNINOVA Organized by: PhD Program on Electrical and Computer Engineering FCTUNL In collaboration with the PhD Program in Electrical and Computer Engineering - FCT-U Coimbra www.Ebook777.com Design, Synthesis, Characterization and Use of Random Conjugated Copolymers 597 functional materials for optoelectronic applications such as organic light-emitting diodes (OLEDs) [2], organic solar cells (OSCs) [3], organic field-effect transistors (OFETs) [4], etc The common feature of these applications consists of using materials with suitable transport and optical properties Conjugated polymers are a class of materials that are gaining great attention by the scientific community due to its potential of providing environmentally safe, flexible, lightweight and inexpensive electronics They show flexibility in synthesis, high yield of charge generation when mixed with electron acceptor materials and good stability Furthermore, they have relatively high absorption coefficients [5] leading to high optical densities in thin solid films Among the conjugated polymers, alternating fluorene copolymers (APFO) [6] and their derivatives have been widely used for efficient organic devices In particular, the APFO-3 polymer has demonstrated efficiencies as high as 4.2% In this polymer the fluorene unit has been used in conjunction with alternating electronwithdrawing (A) and electron-donating (D) groups The structure is a strictly alternating sequence of fluorene and donor-acceptor-donor (DAD) units Conjugated random copolymers are, by far, less used than alternating copolymers for devices fabrication While the disordered structure may hamper the crystallization and decrease the carrier mobility, the presence of different monomer units sequences generate a distribution of energy gaps and increase the light harvesting ability Furthermore an advantage of random copolymers lies in their simplicity of synthesis that consists in a one-pot polymerization step from readily available precursors In this work we report the synthesis and characterization of a novel family of conjugated copolymers based on same the monomeric units of APFO-3 (F: fluorene, T: thiophene, B: benzothiadiazole) but having a pseudorandom structure We applied these new copolymers in solar cells and bright green OLEDs Technological Innovation for Sustainability The development of sustainable energy production is a topic of growing importance in view of the limited supply of fossil fuels, which is expensive financially and not environmentally friendly One of the possible sustainable energy sources is the sun, which makes the development of photovoltaic devices interesting Currently, the market of photovoltaic is dominated by silicon cells technology However, it is still not cheap enough to allow a wide diffusion in the absence of government incentives For this reason huge efforts of research and development have been spent to find alternative and improved solutions Organic devices are lightweight and can be made flexible, opening the possibility for a wide range of applications Our contribution in this field is the development of promising organic materials for photovoltaic and optoelectronic applications In particular, our work revolves around the conjugated polymers that have received considerable attention because of their promising performance In this paper we report the synthesis and characterization of a family of novel conjugated copolymers having a pseudorandom structure The synthesis of random instead of alternating copolymers has the aim to improve the harvesting of the sunlight Indeed, the mixture of possible copolymer resulting from the statistical combination (in condition of equal affinity between the monomers that form copolymers) results in a broadening of the absorption bands due to overlapping of different energy levels This is one of fundamental prerequisites in order to obtain high efficiency photovoltaic devices 598 A Calabrese et al Experimental Three different pseudo-random copolymers (PFB-co-FT, PBT-co-BF, PTF-co-TB) were synthesized by a palladium-catalyzed Suzuki cross-coupling reaction [7] from dibromides and boronic diacids or diesters More details can be found elsewhere [8] The weight-average molecular weight (Mw) and polydispersity index (PDI) were measured by gel permeation chromatography (GPC) using THF as eluent and monodisperse polystyrenes as internal standards UV-Visible absorption spectra of all copolymers was recorded at room temperature with a Lambda 950 spectrophotometer Electrochemical measurements were performed with an Autolab PGSTAT30 potentiostat/galvanostat in a one compartment three-electrode cell working in argonpurged acetonitrile solution with 0.1 M Bu4NBF4 as supporting electrolyte We used a Pt counter electrode, an aqueous saturated calomel (SCE) reference electrode and a Glassy Carbon working electrode which was calibrated against the Fc+/Fc (ferricenium/ferrocene) redox couple, according to IUPAC [9] The films formed on the electrode were analyzed at a scan rate of 200 mV/s OSCs were fabricated by first spin-coating poly(ethylenedioxythiophene:polystyrenesulfonic acid) (PEDOT-PSS) on top of cleaned, pre-patterned indium-tin-oxide (ITO) coated glass substrates as polymer anode (50 nm in thick) The anode polymer film was then annealed at 120°C for 10 The copolymers blended with PCBM in solution were deposited on the top of PEDOT:PSS by spin-coating The cathode consisting of Al (70 nm) was then sequentially deposited on top of the active layer by thermal evaporation in vacuum lower than 10-6 Torr giving a sandwich solar cell structure of ITO/PEDOT:PSS/Copolymer:PCBM/Al Current density-voltage characteristics were measured using a Solar Simulator Abet 2000 (Class A, AM1.5G) All characterization was carried out in an ambient environment OLEDs were fabricated by the same procedure as that of solar cells but in this case the only copolymer in solution were deposited on the top of PEDOT:PSS by spin-coating The corresponding configuration of devices was ITO/PEDOT:PSS/Copolymer/Al Steady-state Photoluminescence (PL) spectra were recorded at room temperature with an Fluorolog spectrofluorometer The steady state current-voltage (I–V) characteristic was recorded by NI-USB 6229 National Instruments acquisition card The electroluminescence (EL) spectra were collected installing the device inside the sample chamber of an IF 650 (Pelkin Elmer) spectrophotometer, working in emission mode, by injecting a current of mA To this purpose a HP E3631 triple output power supply was used as a constant current generator Modeling In order to understand the correlations between property and structure, theoretical calculations were carried out The calculations of HOMO/LUMO distribution of copolymers were performed in two steps The monomeric units was first modeled by using a quantum mechanical Hartree Fock methods [10] In the second step we obtained the geometric optimization of monomers and oligomers by a density functional theory approach [11] The performed calculations showed how HOMO and LUMO positions are affected by electron-donating and electron-withdrawing groups The last occupied orbital is localized primarily on the electron-rich units of the Design, Synthesis, Characterization and Use of Random Conjugated Copolymers 599 molecule (Fluorene and Thiophene) while the first empty orbital is essentially localized on the electron-poor unit (Benzothiadiazole) This means that the molecular orbitals are not extended to the whole structure, but are confined in a limited region of space This has important implications both in the exciton formation and in the charge transfer Following the model results we can conclude that the charge hopping among localized sites is one of the main transport mechanism In order to obtain an electronic transfer between the copolymer and the PCBM, the latter should be close to a benzothiadiazole unit On the other hand, the fact that a partial charge separation already exists, may promote the formation of excitons and extend their lifetime Results and Discussion Material synthesis: The chemical structures of all synthesized copolymers is showed in Fig In the three copolymers, in turn, each F, T, B comonomer unit is alternated to the other two units, which are randomly distributed The weight-average molecular weight (Mw), and polydispersity indices (PDIs) are summarized in Table Fig Chemical structure of the synthesized copolymers Table Molecular weights, optical and electrochemical data of copolymers GPC Entry PFB-co-FT PTF-co-TB PBT-co-BF UV-Vis absorption Cyclic Voltammetry Mw (g/mol) PDI Eg (eV) λmax (nm) ௫ ܧ Ȁܱܯܱܪ 34600 3200 1600 3.00 1.80 2.60 2.38 1.86 1.40 321/460 402/552 326/526 0.81/-5.61 0.51/-5.31 0.21/-5.01 opt (V)/(eV) ௗ ܧ Ȁ ܱܯܷܮEgcv (V)/(eV) (eV) -1.93/-2.87 -1.54/-3.26 -1.40/-3.40 2.74 2.05 1.61 The properties of conjugated polymers are remarkably sensitive to the presence of impurities, which might act as uncontrolled dopants, traps of charge carriers, quenchers of excited states, etc To improve the performance the copolymers solution was treated by ammonia and ethylenediaminetetraacetic acid to remove contaminants such as catalyst residue and side-products from copolymers synthesis (See Table 2) Optical properties: Absorption spectroscopy provides information about the spectral coverage and the magnitude of the optical energy gap that are an important 600 A Calabrese et al parameters in device designing The UV-Vis absorption spectra of the copolymers in thin films are shown in Fig Table Elemental analysis of copolymers at different stages of purification Entry PFB-co-FT PTF-co-TB PBT-co-BF Before purification Pd (ppm) P (ppm) 3400 800 1100 800 30000 9000 After purification Pd (ppm) P (ppm) 10 700 100 800 5000 900 Fig Absorption spectra of films of random copolymers PFB-co-FT (solid curve), PTF-co-TB (dash curve) and PBT-co-BF (dot curve), normalized at the band around 400 nm The optical energy gap of the copolymers was estimated from the onset of absorption and data are reported in Table Electrochemical properties: Cyclic voltammetry (CV) was employed to estimate the HOMO and LUMO energy levels of copolymers Electrochemical data were calculated from the onsets of oxidation and reduction potentials [12] The data obtained are reported in Table and schematized in Fig The electrochemical gap is greater than the optical gap calculated from the UV-Vis spectra This discrepancy is usually related to the charge carriers formation in voltammetric measurements [13] All the copolymers have HOMO and LUMO levels higher than the commonly used [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) acceptor [14] (see Fig 3) PFB-co-FT exhibits the higher molecular weight and the higher energy gap compared to the other two copolymers Furthermore is the copolymer with the highest EHOMOdonor-ELUMOacceptor difference On this basis PFB-co-FT is expected to lead to photovoltaic devices with the better Voc [15] The EHOMOdonorELUMOacceptor difference of PTF-co-TB is lower, but the smaller energy gap could compensate the expected lower Voc with a higher Jsc in designing an efficient solar cell PBT-co-BF, is the copolymer with the lower energy gap and this would makes it the best candidate for OSCs Design, Synthesis, Characterization and Use of Random Conjugated Copolymers 601 5.1 Conjugated Polymer-Based Photovoltaic Devices Photovoltaic devices were fabricated in a typical sandwich structure of glassITO/PEDOT:PSS/Copolymer:PCBM/Al, using copolymers as electron donors and the PCBM as electron acceptor Photovoltaic characterization includes different approaches to optimize the efficiency of the devices The parameters taken into account were: selection of the best solvent, optimization of D:A weight ratio, optimization of the active layer thickness and analyzing annealing effects We have investigated the effects of three different solvents on the photovoltaic performance: Chloroform (CF), Chlorobenzene (CB) and orto-DiChloroBenzene (o-DCB), individually and in a mixture form The copolymer PBT-co-BF showed very low solubility and the tendency to agglomerate in all solvents; this made difficult to obtain a good film and accordingly devices In order to choose the best blend composition, active layers with D:A w/w ratios 1:1, 1:2, 1:3, and 1:4 were studied The photovoltaic parameters of the best cells are summarized in Table Table Photovoltaic parameters of the best solar cells The active area was 0.22cm2 Donor Acceptor PFB-co-FT PTF-co-TB PCBM PCBM D/A ratio C Voc Jsc η Solvent FF (w/w) (mg/ml) (V) (mAcm-2) (%) 1:2 CB:CF (1:1 v/v) 10 0.92 0.90 0.40 0.35 1:4 CB 0.94 3.43 0.31 1.08 Fig shows the J-V curve of the best devices in the dark and under AM 1.5G simulated sunlight at an intensity of 97 mWcm-2 The active layer thickness was 100 nm for all cells The effects of thermal annealing were also studied but it has shown a negative effect in all cases Fig Energy level diagram of the device components (Left); J-V curve of the best solar cells for PFB-co-FT (triangle) and PTF-co-TB (square) in the dark (black) and under illumination (white) (Right) 602 A Calabrese et al 5.2 Light-Emitting Diode Based on Conjugated Polymer Among all copolymers investigated, PFB-co-FT has been recognized as promising material for green emitters due to its photoluminescence efficiency The normalized UV-Vis and PL spectra of copolymer are shown in Fig 4; the absorption maxima is at 460 nm while the emission maxima is at 543 nm The devices was fabricated in a simple structure of glass/ITO/PEDOT:PSS/Copolymer/Al The EL spectra of the device, is showed in Fig Fig Normalized UV-Vis absorption and PL spectra for the PFB-co-FT copolymer in film (Left); Normalized EL spectra of the device recorded at 7.65 V and 1mA (Right) After one month of storage at room temperature the device was re-examined, with identical results and without degradation This outcome confirms the good stability of the film Conclusions In this work we have synthesized a novel family of random copolymers The optical and electrochemical behaviors of the materials were measured and the optoelectronic performance were tested The results clearly demonstrated that there is a correlation between the chemical structure and the HOMO levels determined from electrochemical studies as well as the Voc values determined from photovoltaic devices PTF-co-TB showed interesting photovoltaic properties with Voc of 0.94 V and an efficiency over 1% The PFB-co-FT copolymer was tested as active layer in a simple OLED The device emits in the green and might be a promising candidate for electroluminescent materials due to its excellent luminescent properties, solubility, film-forming property and stability We can conclude that this class of copolymer materials is very promising for optoelectronic applications References Tang, C.W.: Two-layer organic photovoltaic cell Appl Phys Lett 48, 183–185 (1986) Burroughes, J.H., Bradley, D.D.C., Brown, A.R., Marks, R.N., Mackay, K., Friend, R.H., Burns, P.L., Holmes, A.B.: Light-emitting diodes based on conjugated polymers Nature 347, 539–541 (1990) Design, Synthesis, Characterization and Use of Random Conjugated Copolymers 603 Wöhrle, D., Meissner, D.: Organic Solar Cells Adv Mater 3, 129–138 (1991) Drury, C.J., Mutsaers, C.M.J., Hart, C.M., Matters, M., Leeuw, D.M.d.: Low-cost allpolymer integrated circuits Appl Phys Lett 73, 108–110 (1998) Skotheim, T.A., Reynolds, J.R.: Conjugated Polymers: Processing and Applications CRC Press Taylor & Francis Group, USA (2006) Brabec, C.J., Dyakonov, V., Scherf, U.: Organic photovoltaics Materials, device physics and manufacturing technologies Wiley-VCH, Weinheim (2008) Schlüter, A.D.: The tenth anniversary of Suzuki polycondensation (SPC) J Polym Sci A: Polym Chem 39, 1533–1556 (2001) Calabrese, A., Pellegrino, A., Perin, N., Spera, S., Tacca, A., Po, R.: Optical and Electrochemical Properties of Fluorene/Thiophene/Benzothiadiazole Random Copolymers for Photovoltaic Applications (2010) (under sumbission) Gritzner, G., Kuta, J.: Recommendations on reporting electrode potentials in nonaqueous solvents: IUPC commission on electrochemistry Electrochimica Acta 29, 869–873 (1984) 10 Hehre, W.J., Radom, L., Schleyer, P.v.R., Pople, J.A.: Ab Initio Molecular Orbital Theory John Wiley & Sons, Inc., USA (1986) 11 Becke, A.D.: Density-functional exchange-energy approximation with correct asymptotic behavior Phys Rev A 38, 3098–3100 (1988) 12 Hwang, S.-W., Chen, Y.: Synthesis and Electrochemical and Optical Properties of Novel Poly(aryl ether)s with Isolated Carbazole and p-Quaterphenyl Chromophores Macromolecules 34, 2981–2986 (2001) 13 Johansson, T., Mammo, W., Svensson, M., Andersson, M.R., Inganas, O.: Electrochemical bandgaps of substituted polythiophenes J Mater Chem 13, 1316–1323 (2003) 14 Brabec, C.J., Hummelen, J.C., Sariciftci, N.S.: Plastic Solar Cells Adv Funct Mater 11, 15–26 (2001) 15 Brabec, C.J., Cravino, A., Meissner, D., Sariciftci, N.S., Fromherz, T., Rispens, M.T., Sanchez, L., Hummelen, J.C.: Origin of the Open Circuit Voltage of Plastic Solar Cells Adv Funct Mater 11, 374–380 (2001) Optical Transducers Based on Amorphous Si/SiC Photodiodes Manuela Vieira1,2,3, Paula Louro1,2, Miguel Fernandes1,2, Manuel A Vieira1,2, and João Costa1,2 Electronics Telecommunications and Computer Dept., ISEL, Lisbon, Portugal CTS-UNINOVA, Quinta da Torre, 2829-516, Caparica, Portugal DEE-FCT-Universidade Nova de Lisboa, Quinta da Torre, 2829-516, Caparica, Portugal Abstract Amorphous Si/SiC photodiodes working as photo-sensing or wavelength sensitive devices have been widely studied In this paper single and stacked a-SiC:H p-i-n devices, in different geometries and configurations, are reviewed Several readout techniques, depending on the desired applications (image sensor, color sensor, wavelength division multiplexer/demultiplexer device) are proposed Physical models are presented and supported by electrical and numerical simulations of the output characteristics of the sensors Keywords: Amorphous Si/SiC photodiodes, photonic, optoelectronic, image sensors, demultiplexer devices, optical amplifiers Introduction The Tunable optical filters are useful in situations requiring spectral analysis of an optical signal A tunable optical device is a device for wavelength selection such as an add/drop multiplexer (ADM) which enables data to enter and leave an optical network bit stream without having to demultiplex the stream They are often used in wavelength division multiplexing (WDM) systems [1] WDM systems have to accomplish the transient color recognition of two or more input channels in addition to their capacity of combining them onto one output signal without losing any specificity (wavelength and bit rate) Only the visible spectrum can be applied when using polymer optical fiber (POF) for communication [2] So, the demand of new optical processing devices is a request Contribution to Sustainability These sensors are different from the other electrically scanned image sensors as they are based on only one sensing element with an opto-mechanical readout system No pixel architecture is needed The advantages of this approach are quite obvious like the feasibility of large area deposition and on different substrate materials (e.g., glass, polymer foil, etc.), the simplicity of the device and associated electronics, high resolution, uniformity of measurement along the sensor and the cost/simplicity of the detector The design allows a continuous sensor without the need for pixel-level Luis M Camarinha-Matos (Ed.): DoCEIS 2011, IFIP AICT 349, pp 604–611, 2011 © IFIP International Federation for Information Processing 2011 Optical Transducers Based on Amorphous Si/SiC Photodiodes 605 patterning, and so can take advantage of the amorphous silicon technology It can also be integrated vertically, i e on top of a read-out electronic, which facilitates low cost large area detection systems where the signal processing can be performed by an ASIC chip underneath In this paper we present results on the optimization of different multilayered a-SiC:H heterostructures for spectral analysis in the visible spectrum A theoretical analysis and an electrical simulation are performed to support the wavelength selective behavior Device Configuration and Spectral Analysis The semiconductor sensor element is based on single or stacked a-SiC:H p-i-n structures using different architectures, as depicted in Fig All devices were produced by PE-CVD on a glass substrate The simplest configuration is a p-i-n photodiode (NC11) where the active intrinsic layer is a double layered a-SiC:H/a- Si:H thin film In the other the active device consists of a p-i'(a-SiC:H)-n / p-i(a- Si:H)-n heterostructures To decrease the lateral currents, the doped layers (20 nm thick) of NC12 have low conductivities and are based on a-SiC:H [3] Deposition conditions are described elsewhere [4, 5] Full wavelength detection is achieved based on spatially separated absorption of different I TO n wavelengths The blue sensitivity and the red i-Si:H (1000 nm ) transmittance were optimized, respectively, using a i’-SiC:H (200 nm) thin a-SiC:H front absorber (200 nm) with an P I TO optical gap of 2.1 eV and a thick a-SiH back Glass NC11 absorber (1000 nm) with an optical gap around 1.8 eV The thicknesses of both absorbers result from a trade-off between the full absorption of the blue I TO light in the front diode and the green light n across both As a result, both front and back diodes ) nm 00 (10 i-Si:H act as optical filters confining, respectively, the blue P n and the red optical carriers, while the green ones are i’-SiC:H (20 nm ) absorbed across both [6] The devices were P I TO Glass NC12 characterized through spectral response at kHz and photocurrent-voltage measurements To test the sensitivity of the device under different electrical Fig Device configuration and optical bias three modulated monochromatic lights channels: red (R: 626 nm; 51μW/cm2), green (G: 524 nm; 73μW/cm2) and blue (B: 470nm; 115μW/cm2) and their polychromatic combinations (multiplexed signal) illuminated separately the device The generated photocurrent was measured under positive and negative voltages (+1V