DOCSLIB.ORG

Control of Optical Properties of Surfaces for Improved Solar Thermophotovoltaic Systems

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Control of Optical Properties of Surfaces for Improved Solar Thermophotovoltaic Systems Control of Optical Properties of Surfaces for Improved Solar Thermophotovoltaic Systems A Ph.D. dissertation Presented to the Faculty of the School of Engineering and Applied Science University of Virginia In Partial Fulfillment of the requirements for the Degree Doctor of Philosophy (Electrical and Computer Engineering) by Craig Ungaro - 2015 Abstract Alternative energy systems are crucial to meeting the expanding energy needs of the modern world. Unfortunately, the wide spectrum of solar radiation greatly limits the efficiency of photovoltaic systems. Solar thermophotovoltaic (STPV) technology overcomes this problem by tailoring the spectrum of incoming light to better match a photovoltaic cell. This has the potential to greatly increase the efficiency of photovoltaic systems and to help meet future energy demands in an environmentally friendly way. The main challenge in designing efficient STPV systems is controlling the optical properties of the system's light absorbing and emitting surfaces. Through the use of nanostructures, the level of optical control needed to make highly efficient STPV systems will be realized. This work presents a study of the effects of various microscale and nanoscale structures on the absorption and emission spectra of surfaces, as well as their direct application in STPV systems. Computer modeling is used to determine the absorption spectra of various nanostructured surfaces and to predict the efficiency gains from using these structures in an STPV system. The ability to economically fabricate structures for large-area systems is also discussed. A design for a full STPV system utilizing nanostructures for improved efficiency is presented, and the losses in such a system are analyzed. The system is then fabricated, and device performance is compared with simulation. A path towards future improvement of STPV systems is discussed. Additionally, a close collaboration was established with the Center for Nanophase Materials (CNM) at Argonne National Laboratory (ANL), leading to several joint research publications and access to modeling computers and fabrication facilities. Approval Sheet This Ph.D. dissertation is submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Electrical and Computer Engineering) Craig Ungaro This Ph.D. dissertation has been read and approved by the Examining Committee: Professor Mool Gupta, Adviser Professor Robert Weikle, Committee Chair Professor Joshua Choi Professor Lloyd Harriot Dr Stephen Gray, Argonne National Labs Accepted for the School of Engineering and Applied Science: Professor James H. Aylor, Dean, School of Engineering and Applied Science - 2015 ii iii Acknowledgments First, I would like to thank my advisor professor Mool C. Gupta for his encouragement, advice, and technical knowledge as I pursue my Ph.D. degree. I would also like to thank him for offering me the wonderful opportunity to be a part of the unique graduate program at NASA Langley and the National Institute of Aerospace. Secondly, Dr. Stephen Gray of Argonne National Labs was an immense help in this research. I appreciate his technical advice on FDTD modeling, as well as his general guidance on my project. I would also like to thank the NASA Langley Professor program and the NSF IUCRC programs for their support of my research project. This work was performed, in part, at the Center for Nanoscale Materials, a U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences User Facility under Contract No. DE-AC02-06CH1135. A portion of this research was conducted at the Center for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. Lastly, I would like to thank my family and friends for their help and support throughout my time as a graduate student. Contents Contents iv List of Tables vi List of Figures vii List of Symbols and Abbreviationsx 1 Introduction1 1.1 Solar Thermophotovoltaic System Overview..................1 1.2 Importance of Solar Thermophotovoltaic Systems...............2 1.2.1 Absorbing Surface Figure of Merit....................4 1.2.2 Emitting Surface Figure of Merit....................6 1.3 Problem Statement................................8 1.4 Objective.....................................9 2 Literature Review 10 2.1 Photovoltaic Cells for Solar Thermophotovoltaic Systems........... 10 2.2 Absorbing Surfaces................................ 12 2.2.1 Bulk Materials.............................. 13 2.2.2 Nanostructures.............................. 14 2.2.3 Composite Materials........................... 15 2.2.4 Comparison of Absorbing Surfaces................... 16 2.3 Emitting Surfaces................................. 17 2.3.1 Bulk Materials.............................. 18 2.3.2 Nanostructures.............................. 19 2.3.3 Multi-band Emitters........................... 20 2.3.4 Comparison of Emitting Surfaces.................... 21 2.4 Combined Solar Thermophotovoltaic Systems................. 22 3 STPV System Fundamentals and Modeling 24 3.1 STPV System Model............................... 25 3.1.1 The Ray Tracing Method........................ 29 3.2 Surface Emissivity................................ 31 3.2.1 The Transfer Matrix Method (TMM).................. 31 3.2.2 The Finite Difference Time Domain (FDTD) Method......... 33 3.3 Conclusion..................................... 40 4 Modeled Solar Thermophotovoltaic System Design Results 42 4.1 Ideal Solar Thermophotovoltaic System..................... 42 4.1.1 Practical Considerations......................... 44 4.2 Practical System Design............................. 46 iv Contents v 4.2.1 Solar Concentrators............................ 46 4.2.2 System Temperature........................... 47 4.2.3 Emitter to Absorber Area Ratio..................... 47 4.2.4 Absorbing Surfaces............................ 49 4.2.5 Emitting Surfaces............................. 54 4.2.6 Photovoltaic Cells............................. 58 4.2.7 Complete System............................. 59 5 Experimental 65 5.1 Photovoltaic Cells................................. 65 5.2 Absorbing Surface................................. 66 5.2.1 Pseudo-random Nanocone Arrays.................... 66 5.2.2 Glancing Angle Deposition........................ 68 5.3 Emitting Surface................................. 70 5.3.1 Periodic Nanohole Arrays........................ 70 5.3.2 Dielectric/Metal Stacks.......................... 71 5.4 Solar Concentration and Simulation....................... 72 5.4.1 Solar Concentrator System........................ 72 5.4.2 Solar Simulation............................. 74 5.5 STPV System................................... 75 5.5.1 Emitter/Absorber Area Ratio (Aratio).................. 76 5.5.2 Temperature Measurements....................... 77 6 System Characterization and Results 79 6.1 High-efficiency System.............................. 79 6.1.1 High Efficiency System Improvements.................. 83 6.2 Solar System................................... 85 6.2.1 Solar System Improvements....................... 85 7 Conclusions and Future Work 87 7.1 Conclusions.................................... 87 7.2 Future Work.................................... 89 Bibliography 91 Appendices 103 A List of Publications 103 B Published Works 104 List of Tables 2.1 Efficiency of selected absorbing surfaces..................... 16 2.2 Efficiency of selected emitting surfaces...................... 22 4.1 Ebg,Voc, FF, and EQE of PV cells....................... 59 4.2 List of losses in a simulated STPV system.................... 61 4.3 List of default values for system simulations, and the sensitivity of these values. 62 4.4 Optimized efficiency of different system types.................. 62 2 5.1 Measured Voc,Isc, FF, and Pmax of 1.48 cm GaSb PV cells purchased from JX Crystals..................................... 65 5.2 Average reflectivity of microtextured tungsten substrates at 405 nm, 532 nm, 633 nm, 790 nm, 980 nm, and 1064 nm wavelengths............... 67 6.1 Simulated sources of PV cell heating....................... 81 6.2 List of values for experimental system...................... 82 6.3 List of losses in a simulation of the experimental STPV system........ 82 vi List of Figures 1.1 Diagram of flat and cylindrical STPV systems..................2 1.2 Ideal absorption spectra for an absorbing surface................4 1.3 Ideal spectra for an emitting surface for an STPV system...........7 2.1 The optimal temperature for an STPV system at different PV cell bandgaps. 11 3.1 The flow of power through an STPV system................... 26 3.2 The path of an emitted ray through a simple STPV system.......... 30 3.3 A nano-cone array is broken down into a sum of layers of varying eff ..... 32 3.4 Components of the Drude plus four Lorentzian operators plus r for tungsten. 35 3.5 A comparison between simulation and data found in literature for the ab- sorbance of flat tungsten.............................. 36 3.6 FDTD simulation setup.............................. 37 3.7 Change in integrated reflectance due to simulation time............ 39 3.8 Surface plot of nano-cones with randomized placement, height, and radius.. 40 4.1 The maximum efficiency of an ideal STPV system at various temperatures.. 44 4.2 Graphs of emitter-absorber area ratio and system efficiency vs. emitter band- width........................................ 45 4.3 Relative efficiency vs. Aratio for planar STPV system.............
Load more

Recommended publications
  • Research Into Fabrication and Popularization of Organic Thin Film Solar Cells, Chemical Engineering Transactions, 55, 25-30 DOI:10.3303/CET1655005 26
    25 A publication of CHEMICAL ENGINEERING TRANSACTIONS VOL. 55, 2016 The Italian Association of Chemical Engineering Online at www.aidic.it/cet Guest Editors: Tichun Wang, Hongyang Zhang, Lei Tian Copyright © 2016, AIDIC Servizi S.r.l., ISBN 978-88-95608-46-4; ISSN 2283-9216 DOI: 10.3303/CET1655005 Research into Fabrication and Popularization of Organic Thin Film Solar Cells Bin Zhang*a, Yan Lia, Shanlin Qiaob, Le Lic, Zhanwen Wanga a Hebei Chemical & Pharmaceutical College, No. 88 Fangxing Road, Shijiazhuang, Hebei Province, China; b Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao, Shandong Province, China c Shijiazhuang Naienph Chemical Technology Co., Ltd, No. 12 Shifang Road, Shijiazhuang, Hebei Province, China. [email protected] An analysis was conducted herein on the research status of several popular solar cells at the present stage, including silicon solar cell, thin film photovoltaic cell, and dye-sensitized solar cell (DSSC). In doing so, we concluded that the current situations provide a favorable objective environment for the popularization of organic thin film solar cells. Finally, we reviewed the merits and demerits of the organic thin film solar cell together with the major research focus on and progress of it, and summarized obstacles to and development trails of the popularization of organic thin film solar cells. 1. Introduction As the energy crisis further deepens in the 21st century, the existing development level for solar cells has already failed to satisfy increasing social demands for energy. This phenomenon is mainly reflected in the costly high-purity silicon solar panels, in the defects at new amorphous silicon (a-Si) during energy conversion, and in the limited theoretical energy conversion efficiency (around 25%) of silicon solar panels as well.
    [Show full text]
  • Encapsulation of Organic and Perovskite Solar Cells: a Review
    Review Encapsulation of Organic and Perovskite Solar Cells: A Review Ashraf Uddin *, Mushfika Baishakhi Upama, Haimang Yi and Leiping Duan School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney 2052, Australia; [email protected] (M.B.U.); [email protected] (H.Y.); [email protected] (L.D.) * Correspondence: [email protected] Received: 29 November 2018; Accepted: 21 January 2019; Published: 23 January 2019 Abstract: Photovoltaic is one of the promising renewable sources of power to meet the future challenge of energy need. Organic and perovskite thin film solar cells are an emerging cost‐effective photovoltaic technology because of low‐cost manufacturing processing and their light weight. The main barrier of commercial use of organic and perovskite solar cells is the poor stability of devices. Encapsulation of these photovoltaic devices is one of the best ways to address this stability issue and enhance the device lifetime by employing materials and structures that possess high barrier performance for oxygen and moisture. The aim of this review paper is to find different encapsulation materials and techniques for perovskite and organic solar cells according to the present understanding of reliability issues. It discusses the available encapsulate materials and their utility in limiting chemicals, such as water vapour and oxygen penetration. It also covers the mechanisms of mechanical degradation within the individual layers and solar cell as a whole, and possible obstacles to their application in both organic and perovskite solar cells. The contemporary understanding of these degradation mechanisms, their interplay, and their initiating factors (both internal and external) are also discussed.
    [Show full text]
  • Thin Film Cdte Photovoltaics and the U.S. Energy Transition in 2020
    Thin Film CdTe Photovoltaics and the U.S. Energy Transition in 2020 QESST Engineering Research Center Arizona State University Massachusetts Institute of Technology Clark A. Miller, Ian Marius Peters, Shivam Zaveri TABLE OF CONTENTS Executive Summary .............................................................................................. 9 I - The Place of Solar Energy in a Low-Carbon Energy Transition ...................... 12 A - The Contribution of Photovoltaic Solar Energy to the Energy Transition .. 14 B - Transition Scenarios .................................................................................. 16 I.B.1 - Decarbonizing California ................................................................... 16 I.B.2 - 100% Renewables in Australia ......................................................... 17 II - PV Performance ............................................................................................. 20 A - Technology Roadmap ................................................................................. 21 II.A.1 - Efficiency ........................................................................................... 22 II.A.2 - Module Cost ...................................................................................... 27 II.A.3 - Levelized Cost of Energy (LCOE) ....................................................... 29 II.A.4 - Energy Payback Time ........................................................................ 32 B - Hot and Humid Climates ...........................................................................
    [Show full text]
  • Crystalline-Silicon Solar Cells for the 21St Century
    May 1999 • NREL/CP-590-26513 Crystalline-Silicon Solar Cells for the 21st Century Y.S. Tsuo, T.H. Wang, and T.F. Ciszek Presented at the Electrochemical Society Annual Meeting Seattle, Washington May 3, 1999 National Renewable Energy Laboratory 1617 Cole Boulevard Golden, Colorado 80401-3393 NREL is a U.S. Department of Energy Laboratory Operated by Midwest Research Institute ••• Battelle ••• Bechtel Contract No. DE-AC36-98-GO10337 NOTICE This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. Available to DOE and DOE contractors from: Office of Scientific and Technical Information (OSTI) P.O. Box 62 Oak Ridge, TN 37831 Prices available by calling 423-576-8401 Available to the public from: National Technical Information Service (NTIS) U.S. Department of Commerce 5285 Port Royal Road Springfield, VA 22161 703-605-6000 or 800-553-6847 or DOE Information Bridge http://www.doe.gov/bridge/home.html Printed on paper containing at least 50% wastepaper, including 20% postconsumer waste CRYSTALLINE-SILICON SOLAR CELLS FOR THE 21ST CENTURY Y.S.
    [Show full text]
  • Radiation-Thermodynamic Modelling and Simulating the Core of a Thermophotovoltaic System
    energies Article Radiation-Thermodynamic Modelling and Simulating the Core of a Thermophotovoltaic System Chukwuma Ogbonnaya 1,2,* , Chamil Abeykoon 3, Adel Nasser 1 and Ali Turan 4 1 Department of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester M60 1QD, UK; [email protected] 2 Faculty of Engineering and Technology, Alex Ekwueme Federal University, Ndufu Alike Ikwo, Abakaliki PMB 1010, Nigeria 3 Department of Materials, Aerospace Research Institute, The University of Manchester, Manchester M13 9PL, UK; [email protected] 4 Independent Researcher, Manchester M22 4ES, Lancashire, UK; [email protected] * Correspondence: [email protected]; Tel.: +44-016-1306-3712 Received: 31 October 2020; Accepted: 20 November 2020; Published: 23 November 2020 Abstract: Thermophotovoltaic (TPV) systems generate electricity without the limitations of radiation intermittency, which is the case in solar photovoltaic systems. As energy demands steadily increase, there is a need to improve the conversion dynamics of TPV systems. Consequently, this study proposes a novel radiation-thermodynamic model to gain insights into the thermodynamics of TPV systems. After validating the model, parametric studies were performed to study the dependence of power generation attributes on the radiator and PV cell temperatures. Our results indicated that a silicon-based photovoltaic (PV) module could produce a power density output, thermal losses, 2 2 and maximum voltage of 115.68 W cm− , 18.14 W cm− , and 36 V, respectively, at a radiator and PV cell temperature of 1800 K and 300 K. Power density output increased when the radiator temperature increased; however, the open circuit voltage degraded when the temperature of the TPV cells increased.
    [Show full text]
  • Thermal Management of Concentrated Multi-Junction Solar Cells with Graphene-Enhanced Thermal Interface Materials
    applied sciences Article Thermal Management of Concentrated Multi-Junction Solar Cells with Graphene-Enhanced Thermal Interface Materials Mohammed Saadah 1,2, Edward Hernandez 2,3 and Alexander A. Balandin 1,2,3,* 1 Nano-Device Laboratory (NDL), Department of Electrical and Computer Engineering, University of California, Riverside, CA 92521, USA; [email protected] 2 Phonon Optimized Engineered Materials (POEM) Center, Bourns College of Engineering, University of California, Riverside, CA 92521, USA; [email protected] 3 Materials Science and Engineering Program, University of California, Riverside, CA 92521, USA * Correspondence: [email protected]; Tel.: +1-951-827-2351 Academic Editor: Philippe Lambin Received: 20 May 2017; Accepted: 3 June 2017; Published: 7 June 2017 Abstract: We report results of experimental investigation of temperature rise in concentrated multi-junction photovoltaic solar cells with graphene-enhanced thermal interface materials. Graphene and few-layer graphene fillers, produced by a scalable environmentally-friendly liquid-phase exfoliation technique, were incorporated into conventional thermal interface materials. Graphene-enhanced thermal interface materials have been applied between a solar cell and heat sink to improve heat dissipation. The performance of the multi-junction solar cells has been tested using an industry-standard solar simulator under a light concentration of up to 2000 suns. It was found that the application of graphene-enhanced thermal interface materials allows one to reduce the solar cell temperature and increase the open-circuit voltage. We demonstrated that the use of graphene helps in recovering a significant amount of the power loss due to solar cell overheating. The obtained results are important for the development of new technologies for thermal management of concentrated photovoltaic solar cells.
    [Show full text]
  • The Pennsylvania State University the Graduate School Department
    The Pennsylvania State University The Graduate School Department of Chemistry EFFICIENCY ENHANCEMENT IN DYE-SENSITIZED SOLAR CELLS THROUGH LIGHT MANIPULATION A Thesis in Chemistry by Neal M. Abrams © 2005 Neal M. Abrams Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy December 2005 ii The thesis of Neal M. Abrams was reviewed and approved* by the following: Thomas E. Mallouk DuPont Professor of Materials Chemistry and Physics Thesis Advisor Chair of Committee Karl T. Mueller Associate Professor of Chemistry Christine D. Keating Assistant Professor of Chemistry Vincent H. Crespi Professor of Physics Professor of Materials Science and Engineering Ayusman Sen Professor of Chemistry Head of the Department of Chemistry *Signatures are on file in the Graduate School iii ABSTRACT Solar energy conversion is dominated by expensive solid-state photovoltaic cells. As low-cost cells continue to develop, the dye sensitized solar cell has generated considerable interest as an efficient alternative. Although already moderately efficient, this cell offers numerous areas for improvement, both electronically and optically. Solar conversion efficiencies have been studied by modifying optical pathways through these dye-sensitized solar cells, or Grätzel cells. Monochromatic incident-to-photon current efficiency (IPCE) data reveals that an inverse opal photonic crystal or other disordered layer coupled to a nanocrystalline TiO2 layer enhances photocurrent efficiency by illumination from the counter electrode direction. Modifying the cell architecture to allow for illumination through the working electrode yields similar increased enhancements by proper selection of the photonic bandgap. Direct growth of TiO2 inverse opals on a nanocrystalline slab was accomplished by polymer infiltration of the slab, followed by crystal growth and liquid phase deposition.
    [Show full text]
  • Crystalline Silicon Photovoltaic Module Manufacturing
    Crystalline Silicon Photovoltaic Module Manufacturing Costs and Sustainable Pricing: 1H 2018 Benchmark and Cost Reduction Road Map Michael Woodhouse, Brittany Smith, Ashwin Ramdas, and Robert Margolis National Renewable Energy Laboratory NREL is a national laboratory of the U.S. Department of Energy Technical Report Office of Energy Efficiency & Renewable Energy NREL/TP-6A20-72134 Operated by the Alliance for Sustainable Energy, LLC Revised February 2020 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications. Contract No. DE-AC36-08GO28308 Crystalline Silicon Photovoltaic Module Manufacturing Costs and Sustainable Pricing: 1H 2018 Benchmark and Cost Reduction Road Map Michael Woodhouse, Brittany Smith, Ashwin Ramdas, and Robert Margolis National Renewable Energy Laboratory Suggested Citation Woodhouse, Michael. Brittany Smith, Ashwin Ramdas, and Robert Margolis. 2019. Crystalline Silicon Photovoltaic Module Manufacturing Costs and Sustainable Pricing: 1H 2018 Benchmark and Cost Reduction Roadmap. Golden, CO: National Renewable Energy Laboratory. https://www.nrel.gov/docs/fy19osti/72134.pdf. NREL is a national laboratory of the U.S. Department of Energy Technical Report Office of Energy Efficiency & Renewable Energy NREL/TP-6A20-72134 Operated by the Alliance for Sustainable Energy, LLC Revised February 2020 This report is available at no cost from the National Renewable Energy National Renewable Energy Laboratory Laboratory (NREL) at www.nrel.gov/publications. 15013 Denver West Parkway Golden, CO 80401 Contract No. DE-AC36-08GO28308 303-275-3000 • www.nrel.gov NOTICE This work was authored by the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, LLC, for the U.S. Department of Energy (DOE) under Contract No.
    [Show full text]
  • WO 2018/222569 Al 06 December 2018 (06.12.2018) W !P O PCT
    (12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) (19) World Intellectual Property Organization International Bureau (10) International Publication Number (43) International Publication Date WO 2018/222569 Al 06 December 2018 (06.12.2018) W !P O PCT (51) International Patent Classification: KR, KW, KZ, LA, LC, LK, LR, LS, LU, LY, MA, MD, ME, C01B 3/00 (2006.01) MG, MK, MN, MW, MX, MY, MZ, NA, NG, NI, NO, NZ, OM, PA, PE, PG, PH, PL, PT, QA, RO, RS, RU, RW, SA, (21) International Application Number: SC, SD, SE, SG, SK, SL, SM, ST, SV, SY,TH, TJ, TM, TN, PCT/US20 18/034842 TR, TT, TZ, UA, UG, US, UZ, VC, VN, ZA, ZM, ZW. (22) International Filing Date: (84) Designated States (unless otherwise indicated, for every 29 May 2018 (29.05.2018) kind of regional protection available): ARIPO (BW, GH, (25) Filing Language: English GM, KE, LR, LS, MW, MZ, NA, RW, SD, SL, ST, SZ, TZ, UG, ZM, ZW), Eurasian (AM, AZ, BY, KG, KZ, RU, TJ, (26) Publication Langi English TM), European (AL, AT, BE, BG, CH, CY, CZ, DE, DK, (30) Priority Data: EE, ES, FI, FR, GB, GR, HR, HU, IE, IS, IT, LT, LU, LV, 62/5 13,284 31 May 2017 (3 1.05.2017) US MC, MK, MT, NL, NO, PL, PT, RO, RS, SE, SI, SK, SM, 62/5 13,324 31 May 2017 (3 1.05.2017) US TR), OAPI (BF, BJ, CF, CG, CI, CM, GA, GN, GQ, GW, 62/524,307 23 June 2017 (23.06.2017) US KM, ML, MR, NE, SN, TD, TG).
    [Show full text]
  • (2020) How Solar Cell Efficiency Is Governed by the Αμτ Product
    PHYSICAL REVIEW RESEARCH 2, 023109 (2020) How solar cell efficiency is governed by the αμτ product Pascal Kaienburg ,1,2,* Lisa Krückemeier ,1 Dana Lübke ,1 Jenny Nelson ,3 Uwe Rau,1 and Thomas Kirchartz 1,4,† 1IEK5-Photovoltaics, Forschungszentrum Jülich, 52425 Jülich, Germany 2Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, OX1 3PU Oxford, United Kingdom 3Department of Physics and Centre for Plastic Electronics, Imperial College London, London SW7 2AZ, United Kingdom 4Faculty of Engineering and CENIDE, University of Duisburg-Essen, Carl-Benz-Strasse 199, 47057 Duisburg, Germany (Received 18 September 2019; accepted 15 March 2020; published 30 April 2020) The interplay of light absorption, charge-carrier transport, and charge-carrier recombination determines the performance of a photovoltaic absorber material. Here we analyze the influence on the solar-cell efficiency of the absorber material properties absorption coefficient α, charge-carrier mobility μ, and charge-carrier lifetime τ, for different scenarios. We combine analytical calculations with numerical drift-diffusion simulations to understand the relative importance of these three quantities. Whenever charge collection is a limiting factor, the αμτ product is a good figure of merit (FOM) to predict solar-cell efficiency, while for sufficiently high mobilities, the relevant FOM is reduced to the ατ product. We find no fundamental difference between simulations based on monomolecular or bimolecular recombination, but strong surface-recombination affects the maximum efficiency in the high-mobility limit. In the limiting case of high μ and high surface-recombination velocity S,theα/S ratio is the relevant FOM. Subsequently, we apply our findings to organic solar cells which tend to suffer from inefficient charge-carrier collection and whose absorptivity is influenced by interference effects.
    [Show full text]
  • Solar Thermophotovoltaics: Reshaping the Solar Spectrum
    Nanophotonics 2016; aop Review Article Open Access Zhiguang Zhou*, Enas Sakr, Yubo Sun, and Peter Bermel Solar thermophotovoltaics: reshaping the solar spectrum DOI: 10.1515/nanoph-2016-0011 quently converted into electron-hole pairs via a low-band Received September 10, 2015; accepted December 15, 2015 gap photovoltaic (PV) medium; these electron-hole pairs Abstract: Recently, there has been increasing interest in are then conducted to the leads to produce a current [1– utilizing solar thermophotovoltaics (STPV) to convert sun- 4]. Originally proposed by Richard Swanson to incorporate light into electricity, given their potential to exceed the a blackbody emitter with a silicon PV diode [5], the basic Shockley–Queisser limit. Encouragingly, there have also system operation is shown in Figure 1. However, there is been several recent demonstrations of improved system- potential for substantial loss at each step of the process, level efficiency as high as 6.2%. In this work, we review particularly in the conversion of heat to electricity. This is because according to Wien’s law, blackbody emission prior work in the field, with particular emphasis on the µm·K role of several key principles in their experimental oper- peaks at wavelengths of 3000 T , for example, at 3 µm ation, performance, and reliability. In particular, for the at 1000 K. Matched against a PV diode with a band edge λ problem of designing selective solar absorbers, we con- wavelength g < 2 µm, the majority of thermal photons sider the trade-off between solar absorption and thermal have too little energy to be harvested, and thus act like par- losses, particularly radiative and convective mechanisms.
    [Show full text]
  • The Cavity QED Induced Thermophotovoltaic Effect
    Asian J. Energy Environ., Vol. 4, Issues 3-4, (2003), pp. 163-183 The Cavity QED Induced Thermophotovoltaic Effect T. V. Prevenslik 14B, Brilliance Court, Discovery Bay, Hong Kong Email: [email protected] (Received : 15 October 2003 – Accepted : 26 November 2003) Abstract : Thermophotovoltaic (TPV) devices comprise a heater separated from a photocell by a microscopic gap. As the gap is slowly reduced, the photocell current increases while the temperature drops suggesting an underlying thermal mechanism. Conversely, a non-thermal mechanism is indicated since the current remains in phase with rapid gap changes that are faster than the response time of the heater. Both slow and rapid TPV responses may be explained by a theory based on the modification of thermal blackbody (BB) radiation by the gap as a quantum electrodynamics (QED) cavity, the theory called the cavity QED induced TPV effect. By varying the gap, the electromagnetic (EM) resonance of the QED cavity may be adjusted from infrared (IR) to vacuum ultraviolet (VUV) frequencies. At typical heater temperature, the thermal kT energy of the atoms is emitted in the far IR, but the photocells are only sensitive over a small range of frequencies in the near Copyright © 2003 by the Joint Graduate School of Energy and Environment 163 T. V. Prevenslik IR. Thus, for large gaps having EM resonance beyond the far IR, the gap does not modify the BB spectrum, and therefore the photocell current is negligible because of the lack of near IR photons. But if the gap resonance is adjusted to the near IR, the far IR radiation undergoes a frequency up-conversion to produce near IR photons that dramatically increase the photocell current, the frequency up-conversion a consequence of conserving EM energy within cavity QED constraints.
    [Show full text]