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Baranzahi, Amir
Publications (10 of 16) Show all publications
Kanciurzewska, A., Dobruchowska, E., Baranzahi, A., Carlegrim, E., Fahlman, A., Fahlman, M. & Girtu, M. A. (2007). Dye sensitized solar cells with a plastic counter electrode of poly(3,4-ethylene dioxythiophene)-poly(styrenesulfonate) - art. no. 665611. Proceedings of SPIE, the International Society for Optical Engineering, 6656, 65611-65611
Open this publication in new window or tab >>Dye sensitized solar cells with a plastic counter electrode of poly(3,4-ethylene dioxythiophene)-poly(styrenesulfonate) - art. no. 665611
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2007 (English)In: Proceedings of SPIE, the International Society for Optical Engineering, ISSN 0277-786X, E-ISSN 1996-756X, Vol. 6656, p. 65611-65611Article in journal (Refereed) Published
Abstract [en]

n/a

Place, publisher, year, edition, pages
International Society for Optical Engineering; 1999, 2007
Keyword
dye-sensitized solar cells; plastic counter electrode; PEDOT-PSS; I-3(-)/I- electrolyte; photoelectron spectroscopy
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-59148 (URN)000253182100019 ()
Available from: 2010-09-10 Created: 2010-09-09 Last updated: 2017-12-12
Kanciurzewska, A., Dobruchowska, E., Baranzahi, A., Carlegrim, E., Fahlman, M. & Girtu, M. A. (2007). Study on Poly(3,4-ethylene dioxythiophene)-Poly(styrenesulfonate) as a plastic counter electrode in dye sensitized solar cells. Journal of Optoelectronics and Advanced Materials, 9(4), 1052-1059
Open this publication in new window or tab >>Study on Poly(3,4-ethylene dioxythiophene)-Poly(styrenesulfonate) as a plastic counter electrode in dye sensitized solar cells
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2007 (English)In: Journal of Optoelectronics and Advanced Materials, ISSN 1454-4164, E-ISSN 1841-7132, Vol. 9, no 4, p. 1052-1059Article in journal (Refereed) Published
Abstract [en]

Dye sensitized solar cells with PEDOT-PSS coated directly on flexible polyester substrate as counter electrode have been fabricated. The behavior of such plastic counter electrode in the presence of I/I-3 redox electrolyte has been investigated with X-ray photoelectron spectroscopy. We have found that some of iodine species are "trapped" within the PEDOT-PSS layer. The presence of I-3, I-2 and PEDOT charge transfer complexes with iodine species may block the surface of the electrode. Furthermore, the PEDOT may be further oxidized (p-doped) during cell operation, which in turn may cause overoxidation and loss of conductivity in the PEDOT-PSS film. Additionally, the interactions between PEDOT and iodine species may be enlarged because of the partial loss of PSS protective counter ion. That has resulted in decrease of PEDOT-PSS catalytic activity for reduction of I-3 to I in the redox electrolyte and has caused worse cell performance than in case of DSSC with Pt counter electrode.

Keyword
dye-sensitized solar cells, plastic counter electrode, PEDOT-PSS, photoelectron spectroscopy
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-48021 (URN)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-13
Baranzahi, A., Tobias, P., Lloyd Spetz, A., Mårtensson, P., Ekedahl, L. G. & Lundström, I. (1998). Chemical sensors with catalytic metal gates - Switching behavior and kinetic phase transitions. Journal of the Electrochemical Society, 145(10), 3401-3406
Open this publication in new window or tab >>Chemical sensors with catalytic metal gates - Switching behavior and kinetic phase transitions
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1998 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 145, no 10, p. 3401-3406Article in journal (Refereed) Published
Abstract [en]

Rapid transitions in the response of platinum-based chemical sensors occurring at given hydrogen-oxygen concentration ratios are explained by kinetic phase transitions or switching phenomena on the catalytic metal surface. Below the transition point the response of platinum-insulator silicon carbide devices is small and above the transition it is large. It is found that the critical ratio depends on the operation temperature and the properties of the device. Three different cases are identified, namely, injection-, diffusion-, and reaction-rate-determined transitions. At sufficiently large temperatures the transition is injection limited and occurs at the stoichiometric ratio of hydrogen and oxygen in the gas mixture. The implications of the experimental observations on the applications of chemical sensors with catalytic sensing layers are discussed.

Place, publisher, year, edition, pages
Electrochemical Society, 1998
Keyword
chemical sensors, gas sensors, electric sensing devices, catalysis, surface chemistry, MIS devices, electric properties
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-88122 (URN)10.1149/1.1838819 (DOI)000076217000015 ()
Available from: 2013-01-30 Created: 2013-01-30 Last updated: 2017-12-06
Tobias, P., Nakagomi, S., Baranzahi, A., Zhu, R., Lundström, I., Mårtensson, P. & Lloyd Spetz, A. (1998). Electrical characterization of chemical sensors based on catalytic metal gate - Silicon carbide Schottky diodes. In: Silicon Carbide, III-Nitrides and Related Materials, Part 1-2. Paper presented at 7th International Conference on Silicon Carbide, III-Nitrides and Related Materials (ICSCIII-N 97), 31 August - 5 September 1997, Stockholm, Sweden (pp. 1097-1100). Trans Tech Publications, 264-2
Open this publication in new window or tab >>Electrical characterization of chemical sensors based on catalytic metal gate - Silicon carbide Schottky diodes
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1998 (English)In: Silicon Carbide, III-Nitrides and Related Materials, Part 1-2, Trans Tech Publications , 1998, Vol. 264-2, p. 1097-1100Conference paper, Published paper (Refereed)
Abstract [en]

The IV-characteristics of platinum gate Schottky diodes with an interfacial layer of TaSix or Ta depends on gas ambient and they are therefore used as gas sensors, e.g. for combustion engine monitoring. Ideality factors and barrier heights depend on interfacial layers and temperature and are further investigated here. Gas sensitive Schottky diodes on both p-and n-type SIC are shown.

Place, publisher, year, edition, pages
Trans Tech Publications, 1998
Series
Materials Science Forum, ISSN 0255-5476 ; 264-2
Keyword
Schottky diodes; gas sensors; barrier height; ideality factor; interfacial layer
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-88128 (URN)10.4028/www.scientific.net/MSF.264-268.1097 (DOI)000072751000262 ()0-87849-790-0 (ISBN)
Conference
7th International Conference on Silicon Carbide, III-Nitrides and Related Materials (ICSCIII-N 97), 31 August - 5 September 1997, Stockholm, Sweden
Available from: 2013-01-30 Created: 2013-01-30 Last updated: 2014-01-09
Tobias, P., Lloyd Spetz, A., Mårtensson, P., Baranzahi, A., Göras, A. & Lundström, I. (1998). Moving gas outlets for the evaluation of fast gas sensors. In: EUROSENSORS XII, VOLS 1 AND 2. Paper presented at EUROSENSORS XII: 12th European Conference on Solid-State Transducers - 9th UK Conference on Sensors and Their Applications , 13-16 September 1998, Southampton, UK (pp. 761-764). IOP PUBLISHING LTD
Open this publication in new window or tab >>Moving gas outlets for the evaluation of fast gas sensors
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1998 (English)In: EUROSENSORS XII, VOLS 1 AND 2, IOP PUBLISHING LTD , 1998, p. 761-764Conference paper, Published paper (Refereed)
Abstract [en]

It is shown that platinum thin-insula :or-silicon carbide Schottky diodes operated at about 600 degrees C are fast enough to monitor the air fuel ratio in the individual cylinders in the exhaust from a petrol engine. These chemical sensors have time constants of the order of 1 ms. We describe a simple laboratory technique, which can be used to change the gas composition at a chemical sensor within milliseconds. It is based on mechanically oscillating gas outlets placed close to the sensor surface. The properties of and possibilities with such "moving gas outlets" are described.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 1998
Series
SENSORS SERIES
Keyword
Gas sensors; Automotive electronics; Flow; Silicon carbide; High temperature; MIS devices
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-88126 (URN)000077311200185 ()0-7503-0536-3 (ISBN)
Conference
EUROSENSORS XII: 12th European Conference on Solid-State Transducers - 9th UK Conference on Sensors and Their Applications , 13-16 September 1998, Southampton, UK
Available from: 2013-02-07 Created: 2013-01-30 Last updated: 2014-01-09
Tobias, P., Mårtensson, P., Baranzahi, A., Salomonsson, P., Lundström, I., Åbom, L. & Lloyd Spetz, A. (1998). Response of metal-insulator-silicon carbide sensors to different components in exhaust gases. Sensors and actuators. B, Chemical, 47(1-3), 125-130
Open this publication in new window or tab >>Response of metal-insulator-silicon carbide sensors to different components in exhaust gases
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1998 (English)In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 47, no 1-3, p. 125-130Article in journal (Refereed) Published
Abstract [en]

The effects of different components in simulated car exhaust gases on silicon carbide based field effect sensors are studied using a two-level factorial design. Strong effects are observed for H-2, hydrocarbons, and CO. The effects vary with temperature and can possibly be used for a multi-component analysis of exhaust gases.

Place, publisher, year, edition, pages
Elsevier, 1998
Keyword
gas sensors; silicon carbide; high temperatures; factorial design; car exhaust; field effect devices
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-88124 (URN)10.1016/S0925-4005(98)00034-3 (DOI)000074516400020 ()
Available from: 2013-01-30 Created: 2013-01-30 Last updated: 2017-12-06Bibliographically approved
Tobias, P., Baranzahi, A., Lundström, I., Schoner, A., Rottner, K., Karlsson, S., . . . Lloyd Spetz, A. (1998). Studies of the ambient dependent inversion capacitance of catalytic metal oxide silicon carbide devices based on 6H- and 4H-SiC material. In: Silicon Carbide, III-Nitrides and Related Materials, Part 1-2. Paper presented at International Conference on Silicon Carbide, III-Nitrides and Related Materials (ICSCIII-N 97), 31 August - 5 September 1997, Stockholm, Sweden (pp. 1089-1092). Trans Tech Publications, 264-2
Open this publication in new window or tab >>Studies of the ambient dependent inversion capacitance of catalytic metal oxide silicon carbide devices based on 6H- and 4H-SiC material
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1998 (English)In: Silicon Carbide, III-Nitrides and Related Materials, Part 1-2, Trans Tech Publications , 1998, Vol. 264-2, p. 1089-1092Conference paper, Published paper (Refereed)
Abstract [en]

Platinum-oxide-silicon carbide structures change their capacitance upon gas exposure and are used as gas sensors. The decrease of the inversion capacitance within 750 to 900 degrees C due to hydrogen exposure is studied for 4H- and 6H-SiC,:both n- and p-type. A mechanism for the capacitance decrease is suggested which explains also the large change in the conductance of the structures.

Place, publisher, year, edition, pages
Trans Tech Publications, 1998
Series
Materials Science Forum, ISSN 0255-5476 ; 264-2
Keyword
MIS-devices; electric admittance; high temperature; gas sensors; minority carriers
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-88127 (URN)000072751000260 ()0-87849-790-0 (ISBN)
Conference
International Conference on Silicon Carbide, III-Nitrides and Related Materials (ICSCIII-N 97), 31 August - 5 September 1997, Stockholm, Sweden
Available from: 2013-01-30 Created: 2013-01-30 Last updated: 2014-01-09
Tobias, P., Baranzahi, A., Lloyd Spetz, A., Kordina, O., Janzén, E. & Lundström, I. (1997). Fast chemical sensing with metal-insulator silicon carbide structures. IEEE Electron Device Letters, 18(6), 287-289
Open this publication in new window or tab >>Fast chemical sensing with metal-insulator silicon carbide structures
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1997 (English)In: IEEE Electron Device Letters, ISSN 0741-3106, E-ISSN 1558-0563, Vol. 18, no 6, p. 287-289Article in journal (Refereed) Published
Abstract [en]

It is demonstrated that the current-voltage characteristics of platinum-thin insulator silicon carbide diodes react rapidly to changes of the concentration of oxygen and hydrocarbons in the ambient already at temperatures around 500 degrees C-600 degrees C, In this letter, we use moving gas outlets to, for the first time, estimate time constants of the response in the order of a few milliseconds. The short time constants of these sensors make them suitable for applications in combustion monitoring. The new method to modulate gas concentrations rapidly at surfaces has the potential to be a valuable tool for evaluation of device structures for fast chemical sensing.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 1997
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-88139 (URN)10.1109/55.585361 (DOI)A1997XA74300016 ()
Available from: 2013-02-04 Created: 2013-01-30 Last updated: 2017-12-06
Lloyd Spetz, A., Baranzahi, A., Tobias, P. & Lundström, I. (1997). High temperature sensors based on metal-insulator-silicon carbide devices. Physica status solidi. A, Applied research, 162(1), 493-511
Open this publication in new window or tab >>High temperature sensors based on metal-insulator-silicon carbide devices
1997 (English)In: Physica status solidi. A, Applied research, ISSN 0031-8965, E-ISSN 1521-396X, Vol. 162, no 1, p. 493-511Article in journal (Refereed) Published
Abstract [en]

High temperature gas sensors based on catalytic metal-insulator-silicon carbide (MISiC) devices are developed both as capacitors and Schottky diodes. A maximum operation temperature of 1000 degrees C is obtained for capacitors based on 4H-SiC, and all sensors work routinely for several weeks at 600 degrees C. Reducing gases like hydrocarbons and hydrogen lower the flat band voltage of the capacitor and the barrier height of the diode. The time constants for the gas response are in the order of milliseconds and because of this good performance the sensors are tested for combustion engine control. For temperatures around 600 degrees C total combustion occurs on the sensor surface and the signal is high for fuel in excess and low for air in excess. At temperatures around 400 degrees C the response is more linear. The high temperature operation causes interdiffusion of the metal and insulator layers in these devices; and this interdiffusion has been studied. At sufficiently high temperatures the inversion capacitance shows different levels for hydrogen free and hydrogen containing ambients, which is suggested to be due to a reversible hydrogen annealing effect at the insulator-silicon carbide interface.

Place, publisher, year, edition, pages
John Wiley & Sons, 1997
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-88132 (URN)10.1002/1521-396X(199707)162:1<493::AID-PSSA493>3.0.CO;2-C (DOI)A1997XQ45700026 ()
Available from: 2013-01-30 Created: 2013-01-30 Last updated: 2017-12-06
Nakagomi, S., Tobias, P., Baranzahi, A., Lundström, I., Mårtensson, P. & Lloyd Spetz, A. (1997). Influence of carbon monoxide, water and oxygen on high temperature catalytic metal-oxide-silicon carbide structures. Sensors and actuators. B, Chemical, 45(3), 183-191
Open this publication in new window or tab >>Influence of carbon monoxide, water and oxygen on high temperature catalytic metal-oxide-silicon carbide structures
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1997 (English)In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 45, no 3, p. 183-191Article in journal (Refereed) Published
Abstract [en]

High temperature sensors, Schottky diodes and capacitors, based on catalytic metal-oxide-silicon carbide devices are investigated. Reducing gases like hydrogen and other hydrogen containing gases, decrease the barrier height and the flat band voltage, respectively, which is used as the sensor signal. The sensitivity of the devices at 600 degrees C to mixtures of carbon monoxide and oxygen with and without water vapour is studied in this paper. A large binary response of the sensors to carbon monoxide similar to the sensor response to hydrogen gas is observed. Close to the stoichiometric ratio of carbon monoxide and oxygen, the signal changes from a high to a low value corresponding to an excess of carbon monoxide and an excess of oxygen, respectively. When hydrogen is added to a mixture of carbon monoxide and oxygen, the signal changes from a high to a low value at a higher oxygen concentration. Since the response of these devices to hydrogen and hydrogen containing gases is supposed to emanate from hydrogen atoms, the mechanism of the response to carbon monoxide is discussed. The signal to carbon monoxide as well as to hydrogen decreases in the presence of water vapour and the reason for this is discussed.

Place, publisher, year, edition, pages
Elsevier, 1997
Keyword
field effect devices; high temperature; carbon monoxide; water; combustion; silicon carbide
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-88129 (URN)10.1016/S0925-4005(97)00292-X (DOI)000072641900002 ()
Available from: 2013-01-30 Created: 2013-01-30 Last updated: 2017-12-06Bibliographically approved
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