DOCSLIB.ORG

N-Type Silicon Photoelectrochemistry in Methanol: Design of a 10.1

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
N-Type Silicon Photoelectrochemistry in Methanol: Design of a 10.1 Proc. NatL Acad. Sci. USA Vol. 80, pp. 1152-1156, February 1983 Chemistry n-Type silicon photoelectrochemistry in methanol: Design of a 10.1% efficient semiconductor/liquid junction solar cell (solar energy conversion/nonaqueous silicon photoanodes) CHRIS M. GRONET*, NATHAN S. LEWIS*t, GEORGE COGAN0, AND JAMES GIBBONS: *Department of Chemistry, Stanford University, Stanford, California 94305; and *SERA Solar Corporation, Santa Clara, California 95050 Communicated by James P. Coilman, November 22, 1982 ABSTRACT n-Type Si electrodes in MeOH solvent with 0.2 la. The presence of a depletion layer in the semiconductor re- M (1-hydroxyethyl)ferrocene, 0.5 mM (1-hydroxyethyl)ferricenium, sults in the separation of photogenerated electron-hole pairs, and 1.0 M LiClO4 exhibit air mass 2 conversion efficiencies of with the electrons being driven into the bulk and the holes mi- 10.1% for optical energy into electricity. We observe open-circuit grating to the solid/liquid interface. These holes are then con- voltages of0.53 V and short-circuit quantum efficiencies for elec- sumed by a solution reductant, resulting in a flow of current. tron flow ofnearly unity. The fill factor ofthe cell does not decline The voltage difference between the energy at the edge of the significantly with increases in light intensity, indicating substantial semiconductor conduction band and the redox potential of the reduction in efficiency losses in MeOH solvent compared to pre- solution determines the barrier height of the device. Fig. lb vious nonaqueous n-Si systems. Matte etch texturing ofthe Si sur- depicts a possible situation for the interface energetics when face decreases surface reflectivity and increases photocurrent by (9). Here, the fill 50% compared to shiny, polished Si samples. The high values of recombination sites are present at the surface the open-circuit voltage observed are consistent with the presence factor and short-circuit quantum yield may be lower than op- of a thin oxide layer, as in a Schottky meta-insulator-semicon- timal due to the presence of these states at the interface. Thus, ductor device, which yields decreased surface recombination and one method of improving the efficiency of a given semicon- increased values ofopen-circuit voltage and short-circuit current. ductor/liquid junction may be to treat chemically the surface The n-Si system was shown to provide sustained photocurrent at in order to eliminate the deleterious recombination sites. air mass 2 levels (20 mA/cm2) for charge through the interface Another commonly appreciated difficulty in surface barrier of >2,000 C/cm2. The n-Si/MeOH system represents a liquid devices such as Schottky cells and solid/liquid junction cells is junction cell that has exceeded the 10% barrier for conversion of the large value of dark current arising from thermionic emission optical energy into electricity. of carriers at the interface (10, 11). This large dark current leads to values of the open-circuit voltage (VO) at typical solar inten- Nonaqueous solvent systems have been shown to be useful in sities which differ substantially from the barrier height of these suppressingelectrode corrosion orpassivationprocesses at semi- types of devices. For example, for an ideal Si/Au Schottky bar- conductor photoanodes (1-4). However, the efficiencies of rier with a barrier height of 0.8 V, it can be shown thatVO, under most systems under solar irradiation conditions generally have AM1 conditions will be only 0.3 V (12). Clearly, methods of rais- been modest (<6%). This has been ascribed to the presence of ing the values of V,,, in such systems would be highly desirable. states at the liquid/solid interface that act as recombination cen- A technique used in Schottky systems is to introduce a thin in- ters and can seriously limit the efficiency of such systems (4-7). terfacial layer of oxide, creating a metal-insulator-semicon- Thus, although the use ofnonaqueous solvents may improve the ductor (MIS) type cell. This procedure can drastically reduce cell stability, such systems may not be useful unless they can be the dark bucking current (10, 12-16) and thus increase the VOX designed to produce acceptable conversion efficiencies under and efficiency of these devices. solar irradiation conditions. We have applied these concepts to the n-Si/liquid electrolyte In particular, n-type Si cells in ethanol are estimated to yield system. The silicon surface in our studies has a native oxide after about 1% efficiency for conversion of sunlight into electricity etching and exposure to atmosphere (17). The rectifying prop- (5). Because the bulk properties of the materials studied are es- erties ofthis oxide shouldbe sensitive to the etchingprocedure, sentially identical to those used in high-efficiency solid-state so- liquid solvent, and other such factors. We find that n-Si pho- lar cells, we reasoned that the primary source of inefficiency in toelectrodes in MeOH solvent exhibit the high VOZ values and nonaqueous systems must be at the semiconductor/liquid in- efficiencies characteristic of MIS devices, with no evidence of terface. We therefore attempted to exploit chemical treatments the declining fill factors or the poor quantum yields that have that would be effective in changing the chemical and electronic been observed in previous studies of n-Si junctions in non- nature of these interface states. We describe herein the results aqueous solvents. of such experiments, which have resulted in a 10-fold increase in the conversion efficiency of n-Si electrodes in nonaqueous EXPERIMENTAL solvents. Notably, our cells consistently yield 10.1% efficiency for conversion of light to electricity under air mass 2 (AM2) solar The silicon electrodes were fashioned from polished wafers of conditions-a Si-based liquid junction cell that is in excess of 1.3-1.7 ohm-cm resistivity, phosphorus-doped, (100) oriented, the 10% barrier for conversion of optical energy into electricity. single-crystal material obtained from Monsanto. Typical elec- The interface energetics for an ideal semiconductor/liquid trodes consisted of squares 4.0 mm on each side, which were interface (8) at charge transfer equilibrium are presented in Fig. rubbed on the unpolished side with Ga-In eutectic to form an The publication costs of this article were defrayed in part by page charge Abbreviations: AM, air mass; VOX, open-circuit voltage; SCE, standard payment. This article must therefore be hereby marked "advertise- calomel electrode; MIS, metal-insulator-semiconductor. ment" in accordance with 18 U. S. C. §1734 solely to indicate this fact. t To whom reprint requests should be addressed. 1152 Downloaded by guest on September 30, 2021 Chemistry: Gronet et aL Proc. Natl. Acad. Sci. USA 80 (1983) 1153 t solutions of aqueous KCl. The conductivity of 1.0 M LiCl04 in MeOH solution was measured to be 38 mmho/cm. This con- E a b trasts with that of 0.1 M in which is ap- ' ECB (n-Bu4N)C104 EtOH, 0 ECB proximately an order of magnitude lower. The uncompensated ohmic resistance (=50 ohms) present in our cell design in MeOH E Eredox redox E, has not been eliminated or compensated for instrumentally and Ef--- Jl thus makes our present efficiency measurements conservative co by 10-15%. Also, although the experiments described in this EBG EBG ' EVB manuscript were performed in a three-electrode configuration, EVB we expect that efficiencies actually would be higher in a two- CuI Iu, electrode. device of optimized, cell geometry due to less light a- absorption by the solution. + Light sources were a 5.0-mW polarized He/Ne laser (632.8 nm), an ELH-type tungsten halogen bulb with a ground glass diffuser, or an ENH-type bulb with a ground glass diffuser (for FIG. 1. (a) Interfacial energetics at equilibrium for an ideal n-type stability runs). Intensity calibration was performed routinely with semiconductor/liquid junction. The electric field in the semiconductor promotes spatial separation of photogenerated holes and electrons, a Solarex secondary standard Si cell and was periodically veri- providing for net current flow. (b) Interfacial energetics for a particular fied to be within 10% of the value measured with an Eppley distribution of surface states at an n-type semiconductor/liquid junc- thermopile detector. Laser intensities were measured with a tion. Photogenerated carriers are separated as in a; however, the pres- Newport Research (Fountain Valley, CA)' model 815 photom- ence of intermediate levels can promote recombination. This may lead eter. For equilibrium current/voltage measurements, the laser to loss of photocurrent and photovoltage and may result in inefficient beam was expanded with a 5X beam diffuser and collimator from conversion of light into electricity. Aerotech (Pittsburgh). The light intensity was varied by rotation ohmic contact(15). The electrode was then attached to a coil of of a Hoya polarizer in the path of the polarized laser beam. Cu wire with Ag paint, and the Cu wire was passed through a Spectral response curves were obtained with a computer- glass tube to provide insulation from the solution. The exposed controlled system at SERA Solar Corp. (Santa Clara, CA). This Cu and Ag were then sealed with ordinary epoxy cement to ex- apparatus consisted of a Spex .1670 Minimate monochromator pose only the Si to the electrolyte solution. Shiny electrode sur- with a range of 400 to 1,100 nm and provided an average in- faces were obtained by etching in concentrated (48%) aqueous tensity of 1 mW/cm2. The beam was chopped at 13 Hz and was HF for 20 sec followed by a MeOH rinse. Matte electrode sur- referenced to a Si detector (United Detector Technologies, Cul- faces were prepared by exposing unmounted Si to solar cell ver City, CA). Data acquisition and plotting were performed etchant type 200 (Transene, Rowley, MA) for 60 min at 80'C and with a Hewlett-Packard 9826 computer.
Load more

Recommended publications
  • Water-Splitting As Case Study
    inorganics Review First-Principles View on Photoelectrochemistry: Water-Splitting as Case Study Anders Hellman * and Baochang Wang Competence Centre for Catalysis and the Department of Physics, Chalmers University of Technology, 412 96 Gothenburg, Sweden; [email protected] * Correspondence: [email protected]; Tel.: +46-31-72386-9804 Academic Editor: Matthias Bauer Received: 30 March 2017; Accepted: 24 May 2017; Published: 1 June 2017 Abstract: Photoelectrochemistry is truly an interdisciplinary field; a natural nexus between chemistry and physics. In short, photoelectrochemistry can be divided into three sub-processes, namely (i) the creation of electron-hole pairs by light absorption; (ii) separation/transport on the charge carriers and finally (iii) the water splitting reaction. The challenge is to understand all three processes on a microscopic scale and, perhaps even more importantly, how to combine the processes in an optimal way. This review will highlight some first-principles insights to the above sub-processes, in particular as they occur using metal oxides. Based on these insights, challenges and future directions of first-principles methods in the field of photoelectrochemistry will be discussed. Keywords: water splitting; photoelectrochemistry; first-principles 1. Introduction “Water will be the coal of the future” states Cyrus Harding, one of the protagonists in Jules Verne’s novel “The Mysterious Island” [1]. Interestingly this is the conclusion after the protagonists have discussed the fact that the known coal reserves will eventually be depleted. The analogy to today’s crude oil is obvious. Based on the simple fact that it takes millions of years to produce fossil fuel, whereas the extraction, in comparison, is very fast, the depletion of crude oil is certain [2–4], although the exact time remains debatable.
    [Show full text]
  • Hybrid Photoelectrochemical and Photovoltaic Cells for Simultaneous Production of Chemical Fuels and Electrical Power
    ARTICLES https://doi.org/10.1038/s41563-018-0198-y Hybrid photoelectrochemical and photovoltaic cells for simultaneous production of chemical fuels and electrical power Gideon Segev1,2, Jeffrey W. Beeman1,2, Jeffery B. Greenblatt2,3,4 and Ian D. Sharp 1,2,5* Harnessing solar energy to drive photoelectrochemical reactions is widely studied for sustainable fuel production and versatile energy storage over different timescales. However, the majority of solar photoelectrochemical cells cannot drive the overall photosynthesis reactions without the assistance of an external power source. A device for simultaneous and direct production of renewable fuels and electrical power from sunlight is now proposed. This hybrid photoelectrochemical and photovoltaic device allows tunable control over the branching ratio between two high-value products of solar energy conversion, requires relatively simple modification to existing photovoltaic technologies, and circumvents the photocurrent mismatches that lead to significant loss in tandem photoelectrochemical systems comprising chemically stable photoelectrodes. Our proof-of-concept device is based on a transition metal oxide photoanode monolithically integrated onto silicon that possesses both front- and backside photovoltaic junctions. This integrated assembly drives spontaneous overall water splitting with no external power source, while also producing electricity near the maximum power point of the backside photovoltaic junction. The concept that photogenerated charge carriers can be controllably directed to produce electricity and chemical fuel provides an opportunity to significantly increase the energy return on energy invested in solar fuels systems and can be adapted to a variety of architec- tures assembled from different materials. he utilization of solar energy to drive (photo)electrochemical limit considering the solar energy input and the properties of the reactions has been widely studied for sustainable fuel produc- individual components in the system4–8.
    [Show full text]
  • Nanostructured P-Type Semiconductor Electrodes and Photoelectrochemistry of Their Reduction Processes
    energies Review Nanostructured p-Type Semiconductor Electrodes and Photoelectrochemistry of Their Reduction Processes Matteo Bonomo and Danilo Dini * Department of Chemistry, University of Rome “La Sapienza”, 00139 Rome, Italy; [email protected] * Correspondence: [email protected]; Tel.: +39-06-4991-3335 Academic Editor: Peter J. S. Foot Received: 1 April 2016; Accepted: 6 May 2016; Published: 16 May 2016 Abstract: This review reports the properties of p-type semiconductors with nanostructured features employed as photocathodes in photoelectrochemical cells (PECs). Light absorption is crucial for the activation of the reduction processes occurring at the p-type electrode either in the pristine or in a modified/sensitized state. Beside thermodynamics, the kinetics of the electron transfer (ET) process from photocathode to a redox shuttle in the oxidized form are also crucial since the flow of electrons will take place correctly if the ET rate will overcome that one of recombination and trapping events which impede the charge separation produced by the absorption of light. Depending on the nature of the chromophore, i.e., if the semiconductor itself or the chemisorbed dye-sensitizer, different energy levels will be involved in the cathodic ET process. An analysis of the general properties and requirements of electrodic materials of p-type for being efficient photoelectrocatalysts of reduction processes in dye-sensitized solar cells (DSC) will be given. The working principle of p-type DSCs will be described and extended to other p-type PECs conceived and developed for the conversion of the solar radiation into chemical products of energetic/chemical interest like non fossil fuels or derivatives of carbon dioxide.
    [Show full text]
  • Nanowire Photoelectrochemistry
    Nanowire photoelectrochemistry § Jiao Deng1, Yude Su2, , Dong Liu3, Peidong Yang2,4,5,6,*, Bin Liu3,*, Chong Liu1,* 1 Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095, USA 2 Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA 3 School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore 637459, Singapore 4 Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA 5 Department of Materials Science and Engineering, University of California, Berkeley, CA 94720, USA 6 Kavli Energy NanoScience Institute, Berkeley, CA 94720, USA * To whom correspondence may be addressed. Email: [email protected] (P. Y.); [email protected] (B. L.); [email protected] (C.L.). 1 Abstract Recent applications of photoelectrochemistry at the semiconductor/liquid interface provide a renewable route of mimicking natural photosynthesis and yielding chemicals from sunlight, water, and air. Nanowires, defined as one-dimensional nanostructures, exhibit multiple unique features for photoelectrochemical applications and promise better performance as compared to their bulk counterparts. This review aims to provide a summary for the use of semiconductor nanowires in photoelectrochemistry. After a tutorial-type introduction of nanowires and photoelectrochemistry, the summary strives to provide answers to the following questions: 1) How can we interface semiconductor nanowires with other building blocks for enhanced photoelectrochemical responses? 2) How are nanowires utilized for photoelectrochemical half reactions? 3) What are the techniques that allow us to obtain fundamental insights of photoelectrochemistry at single-nanowire level? 4) What are the design strategies for an integrated nanosystem that mimics a closed cycle in artificial photosynthesis? We postulate that this summary will help the readers to evaluate the features of nanowires for photoelectrochemical applications.
    [Show full text]
  • Photoelectrochemistry of Microstructured Silicon Materials for Solar Energy Applications
    PHOTOELECTROCHEMISTRY OF MICROSTRUCTURED SILICON MATERIALS FOR SOLAR ENERGY APPLICATIONS Thesis by James R. Maiolo III In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy California Institute of Technology Pasadena, California 2009 (Defended May 12, 2009) ii © 2009 James R. Maiolo III All Rights Reserved iii Acknowledgements I have a great number of people to thank for a great many contributions that they have made to my life and journey. Anyone who knows me fairly well probably understands that much of who I am is made up of the people I have met and worked with and admired, and that I would certainly not have had such an interesting and full life up to this point without them. I want to start by thanking my wife, Lea. We met right about when I started grad school, and she has stuck with me through everything and has put up with a lot so that I could earn this degree. She made all the tough times easier and all the good times better. Plus, she puts up with me muttering to myself and pacing while I am thinking really hard. My progression as a scientist has been formed and molded by my scientific mentors along the way. It has been an honor working for Nate Lewis these last few years. I honestly do not think I have met anyone so passionate about science and so brilliant. He is an intellectual rock star. I also want to thank my committee for their support. I had the interesting pleasure of having two committees—first Pat Collier and Jonas Peters with Nate, and now Harry Gray, Harry Atwater, and Mitchio Okumura with Nate.
    [Show full text]
  • Thesis Single-Nanoflake Photoelectrochemistry Of
    THESIS SINGLE-NANOFLAKE PHOTOELECTROCHEMISTRY OF MOSE2 THIN FILMS Submitted by Allan Edward Isenberg Department of Chemistry In partial fulfillment of the requirements For the Degree of Master of Science Colorado State University Fort Collins, Colorado Spring 2018 Master’s Committee: Advisor: Justin Sambur James Neilson Jose de la Venta Copyright by Allan Isenberg 2018 All Rights Reserved ABSTRACT SINGLE-NANOFLAKE PHOTOELECTROCHEMISTRY OF MOSE2 THIN FILMS Transition metal dichalcogenide (TMD) thin films represent promising materials for large-area, low-cost, and high-efficiency photoelectrochemical solar energy conversion applications. The outstanding efficiency of bulk TMD crystals has been well documented, which has driven interest in large-area exfoliated TMD thin film devices in recent years. Unfortunately, the solar energy conversion efficiency of nanoflake-coated electrodes is typically much worse than bulk crystal electrodes. It is currently unclear how the high degree of variability among nanoflakes (e.g. area, thickness, types structural features, etc.) contribute to the efficiency gap between nanoflake and bulk electrodes. It is also unclear if exfoliated nanoflakes can achieve the solar conversion efficiencies demonstrated by bulk crystals. The semiconductor-electrolyte dynamics of TMD/iodide photoelectrochemical cells has also been characterized in bulk systems. Bulk TMD electrodes in an iodide electrolyte will form adsorbed oxidation products at the TMD surface, which can cause sharp drops in efficiency in these systems. A clear understanding of how this phenomenon affects the local photoelectrochemical response has not been established. Additionally, it is not clear how the surface reaction kinetics of iodide oxidation products are affected by surface structural features (e.g. basal planes, perimeter-edges, and interior step edges) on TMD nanoflakes.
    [Show full text]
  • Semiconductor Photoelectrochemistry
    NASA Techn ica I Paper 2088 ! January 1983 Semiconductor Photoelectrochemistry A. Martin Buoncristiani and Charles E. Byvik LOAN COW. RETURN TO AFWL TECHWtCAL LlBXAffY i:iETi.AWD AFB, E.M. TECH LIBRARY KAFB, NM 1lll111111111111111111111111 Ill1 1111 NASA 0134938 Technical Paper ,2088 1983 Semiconductor Photoelectrochemistry A. Martin Buoncristiani Christop her Ne wport Co1 lege Newport News, Virginia Charles E. Byvik Langley Research Center Hampton, Virginia NASA National Aeronautics and Space Administration Scientific and Technical Information Branch .I II .I ImI 111111 Use of trade names or names of manufacturers in this report does not constitute an official endorsement of such products or manufacturers, either expressed or implied, by the National Aeronautics and Space Administration. CONTENTS 4 . SPACE-CHARGE DISTRIBUTION IN A SEMICONDUCTOR ELECTRODE ........................ 9 5 . CHARGE TRANSPORT IN A SEMICONDUCTOR ELECTRODE ................................ 20 6 . SATURATION OF PHOTOELECTROLYSIS OF WATER USING A PHOTOELECTROCHEMICAL CELL .................................................. 28 7 . THERMAL PHOTOELECTROCHEMICAL CELL ............................................ 30 8 . ONSET POTENTIAL AND POINT OF ZERO ZETA POTENTIAL ............................. 32 9 . PHOTOPRODUCTION OF HALOGENS .................................................. 34 10 . LAYERED TRANSITION METAL THIOPHOSPHATES ...................................... 37 11. HIGH-EFFICIENCY PHOTOELECTROCHEMICAL SYSTEM .................................. 39 TABLES ..........................................................................
    [Show full text]
  • UNIVERSITY of CALIFORNIA, SAN DIEGO Electrochemistry and Photoelectrochemistry in Carbon Cycle Relevant Energy Systems a Dissert
    UNIVERSITY OF CALIFORNIA, SAN DIEGO Electrochemistry and photoelectrochemistry in carbon cycle relevant energy systems A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Materials Science & Engineering by Mark Justin Llorente Committee in charge: Professor Clifford P. Kubiak, Chair Professor Vitali F. Nesterenko Professor Jan B. Talbot Professor Andrea R.Tao Professor Charles W. Tu 2016 Copyright Mark Justin Llorente, 2016 All rights reserved. Signature Page This dissertation of Mark Justin Llorente is approved, and it is acceptable in quality and form for publication on microfilm and electronically: Chair University of California, San Diego 2016 iii DEDICATION This dissertation is dedicated to my loving lab mates and friends who have taught me time and again that life has the most value when we put in the effort to honestly examine it and in doing so see each other. iv EPIGRAPH A wise man can learn more from a foolish question than a fool can learn from a wise answer. Bruce Lee v TABLE OF CONTENTS Signature Page ............................................................................................................... iii Dedication ...................................................................................................................... iv Epigraph ......................................................................................................................... v Table of Contents .........................................................................................................
    [Show full text]
  • Chapter 7: Photoelectrolysis of Water
    Hydrogen Generation from Irradiated Semiconductor-Liquid Interfaces Krishnan Rajeshwar Center for Renewable Energy Science & Technology (CREST) Department of Chemistry and Biochemistry The University of Texas at Arlington Arlington, TX 76019-0065 E-mail: [email protected] Chapter 7: Hydrogen Generation from Irradiated Semiconductor-Liquid Interfaces 7.1 Introduction and Scope ..........................................................................................3 7.2 Types of Approaches .............................................................................................7 7.3 More on Nomenclature and the Water Splitting Reaction Requirements ...............................................................12 7.4 Efficiency of Photoelectrolysis ............................................................................19 7.5 Theoretical Aspects ..............................................................................................25 7.6 Oxide Semiconductors .........................................................................................29 7.7 Nitrides, Oxynitrides and Oxysulfides .................................................................54 7.8 Metal Chalcogenide Semiconductors ..................................................................57 7.9 Group III-V Compound Semiconductors .............................................................61 7.10 Germanium and Silicon .......................................................................................65 7.11 Silver Halides .......................................................................................................66
    [Show full text]
  • Dye-Sensitized Photoelectrochemical Water Oxidation Through a Buried Junction
    Dye-sensitized photoelectrochemical water oxidation through a buried junction Pengtao Xua,b,c,1, Tian Huanga,b,c,d,e,1, Jianbin Huangd, Yun Yand,2, and Thomas E. Mallouka,b,c,2 aDepartment of Chemistry, The Pennsylvania State University, University Park, PA 16802; bDepartment of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802; cDepartment of Physics, The Pennsylvania State University, University Park, PA 16802; dBeijing National Laboratory for Molecular Science, College of Chemistry and Molecular Engineering, Peking University, 100871 Beijing, China; and eAcademy for Advanced Interdisciplinary Studies, Peking University, 100871 Beijing, China Edited by Richard Eisenberg, University of Rochester, Rochester, New York, and approved May 23, 2018 (received for review March 18, 2018) Water oxidation has long been a challenge in artificial photosyn- are susceptible to both oxidation and hydrolysis (10, 11). Dye de- thetic devices that convert solar energy into fuels. Water-splitting sorption is accelerated at elevated pH (pH > 5). Increasing the pH dye-sensitized photoelectrochemical cells (WS-DSPECs) provide a also lowers the electron injection yield, because the conduction modular approach for integrating light-harvesting molecules with band edge potential of the metal oxide shifts in the cathodic di- water-oxidation catalysts on metal-oxide electrodes. Despite re- rection by about 60 mV per pH unit (12), making electron transfer cent progress in improving the efficiency of these devices by from the photoexcited dye to the metal oxide less favorable. The introducing good molecular water-oxidation catalysts, WS-DSPECs water-oxidation reaction, however, is more thermodynamically have poor stability, owing to the oxidation of molecular compo- favorable at higher pH.
    [Show full text]
  • Dye-Sensitized Nanostructured and Organic Photovoltaic Cells: Technical Review and Preliminary Tests
    Janne Halme Dye-sensitized nanostructured and organic photovoltaic cells: technical review and preliminary tests Master's thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Technology Espoo, February 12, 2002 Supervisor: Professor Peter Lund Instructor: Professor Peter Lund HELSINKI UNIVERSITY OF TECHNOLOGY ABSTRACT OF MASTER'S THESIS Department of Engineering Physics and Mathematics Author: Janne Halme Department: Department of Engineering Physics and Mathematics Major subject: Engineering Physics - Advanced Energy Systems Minor subject: Systems and operations research Title: Dye-sensitized nanostructured and organic photovoltaic cells: technical review and preliminary tests Väriaineherkistetyt nanorakenteiset ja orgaaniset aurinkosähkökennot: Title in Finnish: tekninen kirjallisuuskatsaus ja alustavia kokeita Chair: Tfy-56, Advanced Energy Systems Supervisor: Professor Peter Lund Instructor: Professor Peter Lund The solar electricity is presently a rapidly growing but often relatively expensive renewable energy form. Recently however, new molecular photovoltaic (PV) materials have been developed, which could enable a production of low-cost solar cells in the future. The thesis begins with a discussion of the current status of the PV technology and a short introduction to the different PV technologies and to the basics of photovoltaics. The dye-sensitized solar cell (DSSC) is an electrochemical solar cell where light absorption occurs by dye molecules attached to a nanostructured TiO2 electrode. An introduction to the DSSC is given including a short description of the operating principle of the cell and a discussion of the physical and chemical processes behind it. A systematic literature review is done on the materials and most essential preparation methods of the standard DSSC.
    [Show full text]
  • Dye Sensitized Solar Cells
    Int. J. Mol. Sci. 2010, 11, 1103-1113; doi:10.3390/ijms11031103 OPEN ACCESS International Journal of Molecular Sciences ISSN 1422-0067 www.mdpi.com/journal/ijms Review Dye Sensitized Solar Cells Di Wei NOKIA Research Centre c/o University of Cambridge, Broers Building, 19 JJ Thompson Avenue, CB3 0FA, Cambridge, UK; E-Mail: [email protected] Received: 2 February 2010; in revised form: 2 March 2010 / Accepted: 4 March 2010 / Published: 16 March 2010 Abstract: Dye sensitized solar cell (DSSC) is the only solar cell that can offer both the flexibility and transparency. Its efficiency is comparable to amorphous silicon solar cells but with a much lower cost. This review not only covers the fundamentals of DSSC but also the related cutting-edge research and its development for industrial applications. Most recent research topics on DSSC, for example, applications of nanostructured TiO2, ZnO electrodes, ionic liquid electrolytes, carbon nanotubes, graphene and solid state DSSC have all been included and discussed. Keywords: photoelectrochemistry; dye sensitized solar cells (DSSC) 1. Introduction Photoelectrochemical solar cell is generally composed of a photoactive semiconductor working electrode and counter electrode made of either metal (e.g., Pt) or semiconductors. Both electrodes are immersed in the electrolyte containing suitable redox couples. If the semiconductor-electrolyte interface (SEI) is illuminated with a light having energy greater than the bandgap of the semiconductor, photogenerated electrons/holes are separated. The photogenerated minority carriers arrive at the interface of the semiconductor-electrolyte. Photogenerated majority carriers accumulate at the backside of the semiconductor. With the help of a charge-collecting substrate, photogenerated majority carriers are transported via a load to the counter electrode where these carriers electrochemically react with the redox electrolyte.
    [Show full text]