Basic Research Needs for Solar Energy Utilization - Office of ...

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ealize an efficient artificial photosynthetic system for solar fuels production. Developing such an integrated system would have a major impact on energy supply worldwide, as well as provide a new paradigm for designing all new molecular energy conversion systems. REFERENCES B. Rybtchinski, L.E. Sinks, and M.R. Wasielewski, “Combining Light-harvesting and Charge Separation in a Self-assembled Artificial Photosynthetic System based on Perylenediimide Chromophores,” J. Am. Chem. Soc. 126, 12268–12269 (2004). G. Steinberg-Yfrach, J.-L. Rigaud, E.N. Durantini, A.L. Moore, D. Gust, and T.A. Moore, “Light-driven Production at ATP Catalyzed by F0F1-ATP Synthase in an Artificial Photosynthetic Membrane,” Nature (London) 392, 479–482 (1998). 144
ACHIEVING DEFECT-TOLERANT AND SELF-REPAIRING SOLAR CONVERSION SYSTEMS No molecule-based solar energy conversion system, including photosynthesis, or system made from amorphous silicon or many other thin-film inorganic materials, currently maintains its performance in sunlight for 20–30 years. Defect formation mechanisms in photovoltaic materials, as well as self-repair and photo-protection mechanisms in photosynthesis, must be understood and implemented in real-world systems. Achieving defect-tolerant or active selfrepair devices would enable the practical utilization of many types of solar energy conversion systems that currently are too unstable to last for the required 20–30 years of operation to produce cost-effective solar electricity or fuels. EXECUTIVE SUMMARY Insensitivity of performance to manufacturing and usage-induced defects over a pre-specified range is an inherent requirement of system design, specification, affordability, and performance for extended periods of time in real-world systems. By way of contrast, biological systems, such as photosynthesis, have built-in repair mechanisms that can restore useful function following damage to the system. Identifying and implementing fault-tolerant and/or self-repair paradigms in inorganic and organic systems is a “grand-challenge”-level basic science enterprise that would revolutionize not only the solar energy conversion field but a wide variety of other application areas as well. To ensure that complex systems designed for solar fuels production maintain their efficiency over long lifetimes, the following research directions must be addressed: (1) understand the factors affecting interactions between a large variety of possible structural defects and charge carriers in inorganic PV materials; (2) understand repair and photoprotection mechanisms in natural photosynthesis; (3) control three-dimensional architectures in nanoscale materials to promote redundancy and distributed function as a strategy to tolerate defects; (4) explore assembly-disassembly strategies as a mode of self-repair; and (5) develop active repair molecules that specifically identify and target defects and repair them. SUMMARY OF RESEARCH DIRECTION The current highest efficiency (~35%) solar cells are the nearly perfect epitaxially grown compound semiconductor multi-junction structures that collect light across the solar spectrum but are both sensitive to defects and prohibitively expensive to mass-produce. There is thus a critical need to discover, design, and synthesize new materials and structures with solar energy conversion properties that are intrinsically insensitive to defects (point and line defects, grain boundaries, impurity/composition, disorder, morphology, and interface defects) and thus relax the strict requirements on manufacturing of nearly perfect material structures. Since absorption of solar photons and separating the resulting electron-hole pair (usually exciton) is the fundamental basis for conversion to electricity, designing materials and structures that inherently permit reduction of defects or allow charge separation and transport mechanisms tolerant of defects is the fundamental challenge faced in realizing high-performance and affordably manufacturable photovoltaic (PV) solar cells. An example of the defect-reduction approach is the use of selective growth on nanoscale spatial templates, which allows relief of the lattice 145
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On the Cover: One route to harvesti
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Revisions, September 2005 p ix, par
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CONTENTS (CONT.) Appendix 4: Additi
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OEC oxygen-evolving complex PCET pr
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viii
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thin films, organic semiconductors,
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genetic sequencing, protein product
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INTRODUCTION The supply and demand
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showing promise to overcome them. T
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GLOBAL ENERGY RESOURCES 7
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energy can be exploited on the need
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BASIC RESEARCH CHALLENGES FOR SOLAR
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CONVERSION OF SUNLIGHT INTO ELECTRI
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PHYSICS OF PHOTOVOLTAIC CELLS Inorg
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Figure 4 Learning curve for PV prod
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Needs of Direct-gap, Thin-film Phot
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Figure 6 Current record efficiencie
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devices. The molecules and material
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Figure 8 Structure for high-efficie
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One critical property of the photoa
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PHOTOELECTROCHEMICAL STORAGE CELLS
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BASIC RESEARCH CHALLENGES FOR SOLAR
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information about the proteins that
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convert it into H2 and liquid fuels
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charge separation ensures highly ef
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Efficient Photo-initiated Charge Se
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artificial RCs, have proven to be i
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CATALYSTS FOR CO2 REDUCTION Photo-d
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Upon photoexcitation, the electron
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(5) determining the physical and ch
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following challenges must be met: (
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A.F. Heyduk and D.G. Nocera, “Hyd
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J. Seth, V. Palaniappan, R.W. Wagne
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THREE TYPES OF CONCENTRATED SOLAR
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Solar Thermal to Electric Energy Co
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Tm = mean temperature Z = measure o
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control and further diode developme
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An overview of solar thermochemical
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for electron and phonon band struct
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coefficient. The thermal conductivi
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J.J. Greffet, R. Carminati, K. Joul
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CROSS-CUTTING RESEARCH CHALLENGES B
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ange of time and length scales span
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Research Issues Advances in the syn
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Advances across several science fro
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Figure 19 Transparent conductive el
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Carrier generation, relaxation, and
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E. Hutter and J.H. Fendler, “Expl
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PRIORITY RESEARCH DIRECTIONS Revolu
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RESEARCH DIRECTIONS Several paths e
Page 108 and 109: Multiple Energy Level Solar Cells I
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Page 114 and 115: A.J. Nozik, “Quantum Dot Solar Ce
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Page 118 and 119: Figure 30 Schematic diagram (right)
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Page 124 and 125: Figure 32 One important example of
Page 126 and 127: interface for charge separation. Fo
Page 128 and 129: • Light harvesting, • Advanced
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Page 132 and 133: Multicomponent structures are often
Page 134 and 135: REFERENCES A.J. Bard and M.A. Fox,
Page 136 and 137: PLANT PRODUCTIVITY AND BIOFUEL PROD
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Page 142 and 143: SUMMARY OF RESEARCH DIRECTION The k
Page 144 and 145: developing multi-electron catalytic
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Page 150 and 151: low toxicity, and processibility. T
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Page 154 and 155: largely unknown are the fundamental
Page 156 and 157: nanostructure design, and developme
Page 160 and 161: Figure 46 Defect-tolerant solar cel
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Page 164 and 165: H2SO4 at 1,130K, and the University
Page 166 and 167: the sequestration step, these solar
Page 168 and 169: P. von Zedtwitz and A. Steinfeld,
Page 170 and 171: The continued advances in energy- a
Page 172 and 173: for the detailed understanding and
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Page 176 and 177: A shortcoming of this approach is t
Page 178 and 179: of ~2.4 at 300K and quantum-dot PbT
Page 180 and 181: High-throughput Experimental Screen
Page 182 and 183: Solar Concentrators and Hot Water H
Page 184 and 185: G. Chen, M.S. Dresselhaus, J.-P. Fl
Page 186 and 187: Materials and Processing Methods to
Page 188 and 189: materials and fabrication approache
Page 190 and 191: multi-electron H2O and CO2 activati
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Page 196 and 197: and quantum dots. Quantum dots are
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Page 202 and 203: Flux (mA/eV.cm2 Flux (mA/eV.cm ) 2
Page 204 and 205: Table 1 Worldwide PV Module Product
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Table 2 Are There Enough Materials
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passivating window and back-surface
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R.R. King, C.M. Fetzer, K.M. Edmond
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currently accounting for only a sma
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Anaerobic Digestion One gasificatio
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Electrolysis is the process for bre
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alkaline electrolyzers require a mi
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maintenance costs of the small prod
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P. Courty, P. Chaumette, and C. Rai
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212
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periods and extend the system opera
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When ηopt < 1, Equation (2) become
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Receiver & Power Conversion Unit So
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Figure 77 General concept of solar-
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Other areas whose development could
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THERMOPHOTOVOLTAICS Thermophotovolt
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N. Benz and Th. Kuckelkorn, “A Ne
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R.A. Sherif, H.L. Cotal, R.R. King,
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Sub-panelists Edmond Amouyal, Centr
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Terry Tritt, Clemson University Joh
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Plenary Closing Session — Wednesd
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Panel 1C (Photoelectrochemistry)
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Agenda for Solar Fuels Breakout Ses
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Tuesday, April 19, 2005, 8:00 a.m.
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Wednesday, April 20, 2005, 8:00 a.m
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Wednesday, April 20, 2005, 8:00 a.m
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250
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R. Corkish, S. Kettemann, and J. Ne
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T. Polivka and V. Sundstrom, “Ult
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microscopy, 81, 85, 101, 155-157, 1
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