The Experts below are selected from a list of 219 Experts worldwide ranked by ideXlab platform
A Stoffel - One of the best experts on this subject based on the ideXlab platform.
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single chip condenser microphone using porous silicon as sacrificial layer for the air gap
Sensors and Actuators A-physical, 2001Co-Authors: W Kronast, B Muller, W Siedel, A StoffelAbstract:Abstract A single-chip IC-compatible silicon condenser microphone with a highly sensitive silicon nitride diaphragm and a rigid monocrystalline silicon Counterelectrode with acoustic holes was designed and built. Porous silicon with its high dissolution rate in 1% KOH was used as an auxiliary sacrificial layer in combination with sputtered SiO 2 to define the air gap. This results in low parasitic capacitances and a microphone structure where the diaphragm is coplanar with its suspensions. The rigid backelectrode is undistorted, the diaphragm under low tensile stress, a prerequisite for high sensitivity. Microphones of different dimensions of round and square electrodes with single diaphragms and diaphragm arrays were built and packaged in round chip carriers. The open loop sensitivity is in the mV/Pa range depending on the type of microphone. The frequency response goes beyond 25 kHz for an air gap of 1.3 μm.
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single chip condenser microphone using porous silicon as sacrificial layer for the air gap
International Conference on Micro Electro Mechanical Systems, 1998Co-Authors: W Kronast, B Muller, W Siedel, A StoffelAbstract:A single-chip IC-compatible silicon condenser microphone with a highly sensitive silicon nitride membrane and a rigid monocrystalline silicon Counterelectrode with acoustic holes was designed and built. Porous silicon with its high dissolution rate in 1% KOH was used as an auxiliary sacrificial layer in combination with sputtered SiO/sub 2/ to define the air gap. This results in low parasitic capacitances and a microphone structure where the membrane is coplanar with its suspensions. The rigid backelectrode is undistorted, the membrane under low tensile stress, a prerequisite for high sensitivity. Microphones of different dimensions of round and square electrodes with single membranes and membrane arrays were built and packaged in round chip carriers. The open loop sensitivity is in the mV/Pa range depending on the type of microphone. The frequency response goes beyond 25 kHz for an air gap of 1.3 /spl mu/m.
W Kronast - One of the best experts on this subject based on the ideXlab platform.
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single chip condenser microphone using porous silicon as sacrificial layer for the air gap
Sensors and Actuators A-physical, 2001Co-Authors: W Kronast, B Muller, W Siedel, A StoffelAbstract:Abstract A single-chip IC-compatible silicon condenser microphone with a highly sensitive silicon nitride diaphragm and a rigid monocrystalline silicon Counterelectrode with acoustic holes was designed and built. Porous silicon with its high dissolution rate in 1% KOH was used as an auxiliary sacrificial layer in combination with sputtered SiO 2 to define the air gap. This results in low parasitic capacitances and a microphone structure where the diaphragm is coplanar with its suspensions. The rigid backelectrode is undistorted, the diaphragm under low tensile stress, a prerequisite for high sensitivity. Microphones of different dimensions of round and square electrodes with single diaphragms and diaphragm arrays were built and packaged in round chip carriers. The open loop sensitivity is in the mV/Pa range depending on the type of microphone. The frequency response goes beyond 25 kHz for an air gap of 1.3 μm.
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single chip condenser microphone using porous silicon as sacrificial layer for the air gap
International Conference on Micro Electro Mechanical Systems, 1998Co-Authors: W Kronast, B Muller, W Siedel, A StoffelAbstract:A single-chip IC-compatible silicon condenser microphone with a highly sensitive silicon nitride membrane and a rigid monocrystalline silicon Counterelectrode with acoustic holes was designed and built. Porous silicon with its high dissolution rate in 1% KOH was used as an auxiliary sacrificial layer in combination with sputtered SiO/sub 2/ to define the air gap. This results in low parasitic capacitances and a microphone structure where the membrane is coplanar with its suspensions. The rigid backelectrode is undistorted, the membrane under low tensile stress, a prerequisite for high sensitivity. Microphones of different dimensions of round and square electrodes with single membranes and membrane arrays were built and packaged in round chip carriers. The open loop sensitivity is in the mV/Pa range depending on the type of microphone. The frequency response goes beyond 25 kHz for an air gap of 1.3 /spl mu/m.
Michael Gratzel - One of the best experts on this subject based on the ideXlab platform.
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alternative bases to 4 tert butylpyridine for dye sensitized solar cells employing copper redox mediator
Electrochimica Acta, 2018Co-Authors: Parnian Ferdowsi, Yasemin Saygili, Shaik M Zakeeruddin, Javad Mokhtari, Michael Gratzel, Anders Hagfeldt, Michael Gratzel, Ladislav KavanAbstract:Abstract Novel facile synthetic protocol is developed to prepare electrochemically and optically clean Cu(tmby)2TFSI and Cu(tmby)2TFSI2 in a mixture (tmby = 4,4,6,6-tetramethyl-2,2-bipyridine; TFSI = trifluoromethylsufonylimide). This pure Cu(II/I) redox mediator exhibits improved charge-transfer rate at the Counterelectrode (PEDOT) and faster diffusion transport in the solution. Four pyridine derivatives: 4-tert-butylpyridine, 2,6-bis-tert-butylpyridine, 4-methoxypyridine and 4-(5-nonyl)pyridine are evaluated as electrolyte additives. Base-specific electrochemical properties of the redox mediator are found for Cu(tmby)22+/+, but not for Co(bpy)33+/2+ which is used as control system. Due to steric hindrance, 2,6-bis-tert-butylpyridine has the smallest influence on the mediator's electrochemistry, but is also ineffective for the VOC enhancement through TiO2 conduction band upshift. Charge-transfer rates at PEDOT surface and diffusion resistances correlate with the basicity (pKa) of the used pyridine derivatives. The dye (Y123)-sensitized solar cells are evaluated by solar conversion performance in addition to electron lifetime, charge extraction and long-term stability tests. The optimization of pyridine bases for the Cu-mediated solar cells represents interplay of basicity and coordination ability. In turn, this allows for tuning of the charge transfer rate at Counterelectrode and the mass transport in the electrolyte solution. The 4-(5-nonyl)pyridine is outperforming all the remaining bases in performance metrics of the corresponding solar cells.
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application of highly ordered tio2 nanotube arrays in flexible dye sensitized solar cells
ACS Nano, 2008Co-Authors: Daibin Kuang, Shaik M Zakeeruddin, Jeremie Brillet, Peter Chen, Masakazu Takata, Satoshi Uchida, Hidetoshi Miura, Kohichi Sumioka, Michael GratzelAbstract:TiO2 nanotube arrays prepared by electrochemical anodization of Ti foils show impressive light to electricity conversion efficiency in the dye-sensitized solar cells (DSCs). The length of the TiO2 nanotube arrays (5−14 µm) was controlled by varying the anodization time from 2 to 20 h. The influence of nanotube lengths on the photovoltaic performance of DSCs was investigated by impedance. A flexible DSC using TiO2 nanotube arrays on a Ti foil as a working electrode and polyethylene naphthalate (ITO/PEN) as Counterelectrode in combination with solvent-free ionic liquid electrolyte achieved 3.6% photovoltaic conversion efficiency under simulated AM 1.5 sunlight.
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low cost photovoltaic modules based on dye sensitized nanocrystalline titanium dioxide and carbon powder
Solar Energy Materials and Solar Cells, 1996Co-Authors: Michael GratzelAbstract:A new type of photovoltaic module based on monolithically series connected dye sensitized photoelectrochemical cells is described. Each solar cell element consists of three porous layers on a transparent conducting substrate, namely a photoelectrode of dye sensitized nanocrystalline TiO2 (anatase), a spacer of electrically insulating, light reflecting particles of TiO2 (rutile), and a Counterelectrode of graphite powder and carbon black. The pores of these layers are filled with a redox electrolyte containing iodide for hole transport between photo- and Counterelectrode. The monolithic series connection on the transparent conducting substrate, e.g., SnO2 coated glass, is achieved by simple overlap of each carbon Counterelectrode with the back contact of the adjacent photoelectrode. Such modules may be produced in a continuous non-vacuum process by simple printing techniques. In this paper we present the first results on energy conversion efficiency and long term stability obtained with this new type of solar cell.
Takaya Kubo - One of the best experts on this subject based on the ideXlab platform.
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durability of electrochromic windows fabricated with carbon based Counterelectrode
SPIE's International Symposium on Optical Science Engineering and Instrumentation, 1999Co-Authors: Tsuyoshi Asano, Takaya Kubo, Yoshinori NishikitaniAbstract:A tungsten oxide film has been widely employed as an electrochromic material dye to its great electrochemical durability. Durability of carbon materials as electrodes have been more clearly verified in many practical use, a lithium ion battery and an electric double layer capacitor, for example. We then focused on a large electric double layer capacitance and the electrochemical durability in carbon materials. The chief purpose of this paper is to examine electro-optical performance and durability of the electrochromic windows (ECW) fabricated with the carbon- based electrode. The ECWs have been tested for durability under various weather conditions. Most of the tests were carried out on the ECWs with UV-cut filters installed. The filters allowed us to improve the ECW durability greatly. Main results are as follows: (1) we were successful in developing carbon-based electrodes for ECWs and in fabricating an ECW (a carbon-based electrode/a polymeric solid electrolyte/a tungsten oxide electrode), (2) the utilization of the carbon-based electrode increased the ECW durability against high temperature, UV radiation, heat cycle and so forth, and (3) their electrochromic performance were found out to be sufficiently high enough for architectural and automotive purposes.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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thermal and optical behavior of electrochromic windows fabricated with carbon based Counterelectrode
Electrochimica Acta, 1999Co-Authors: Yoshinori Nishikitani, Tsuyoshi Asano, Soichi Uchida, Takaya KuboAbstract:We proposed a carbon-based Counterelectrode for electrochromic windows (ECWs) and fabricated a new solid-state ECW consisting of an indium tin oxide electrode (ITO, IN2O3:SN)/a WO3 film/a polymeric solid electrolyte (PSE)/a carbon-based Counterelectrode. The carbon-based Counterelectrode is a series of arrays of carbon material dots formed on an ITO substrate and is virtually transparent in a visible region, Those carbon dots play a part in the formation of an electric double layer in an electrochromic reaction of the ECW. The electric double layer capacitance of the Counterelectrode increases linearly as a function of carbon-dot covering percentage on the ITO substrate. Maximum differential optical density of the ECW increases with the covering percentage of the carbon dots up to a point and levels off for further increase in the covering percentage. The response time of coloration decreases with temperatures, which is caused chiefly by the temperature dependence of an ionic conductivity of the PSE. The behavior of ECWs is explained well with a simple equivalent-circuit comprising two capacitors corresponding to the WO3, film and the carbon-based Counterelectrode, an electric resistor of the PSE and a power source connected in series.
Tzuchien Wei - One of the best experts on this subject based on the ideXlab platform.
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electroless deposition of platinum on indium tin oxide glass as the Counterelectrode for dye sensitized solar cells
Materials Chemistry and Physics, 2010Co-Authors: Chihming Chen, Chiahsien Chen, Shengjye Cherng, Tzuchien WeiAbstract:Abstract A platinum (Pt) layer is electroless-deposited on indium tin oxide (ITO) glass substrate as the Counterelectrode for dye-sensitized solar cells (DSSCs). Compared with other methods of depositing Pt layer, electroless deposition is simple, low-temperature, and easy to scale-up for industrial application. The Pt concentration of the electroless plating solution is found to play an important role in the cell performance. With increasing the Pt concentration, i.e. the Pt loading on the ITO surface, the resultant Pt layer exhibits a porous structure. Owing to the porous structure, the Pt layer can provide more active surface area for triiodide reduction and thus reduces the charge-transfer resistance. The cell performance is promoted accordingly with increasing the Pt concentration. Energy conversion efficiency of 6.46%, short-circuit current density of 15.04 mA cm −2 , open-circuit voltage of 0.68, and fill factor of 0.63 can be achieved for the DSSC employing electroless-Pt Counterelectrode.
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poly n vinyl 2 pyrrolidone capped platinum nanoclusters on indium tin oxide glass as Counterelectrode for dye sensitized solar cells
Applied Physics Letters, 2006Co-Authors: Tzuchien Wei, C C Wan, Y Y WangAbstract:Poly(N-vinyl-2-pyrrolidone)-capped platinum nanoclusters were deposited on indium tin oxide glass as a Counterelectrode for dye-sensitized solar cells using a “two-step dip coating” process at room temperature. Compared to sputtered-Pt electrodes, an electrode produced by this technique exhibited ultralow Pt-loading at 4.89μg∕cm2 and an acceptable charge-transfer resistance of 5.66Ωcm2. Current-voltage characteristics of the DSSC at this stage stand at 0.66V on VOC, 10.5mA∕cm2 on ISC, 0.41 on fill factor, and 2.84% cell efficiency under AM1.5, 100mW∕cm2 illumination.
