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

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carrier injection between the individual cells has received little attention. Use of colloidal metals to fulfill this function has proven to be surprisingly successful; the amount of metal required is minimal, and beneficial field-enhancement effects improve the absorption properties of the surrounding medium. Although the basic effects are understood, significant improvements in device performance depend upon a far more detailed understanding of the properties of these and related species when they are embedded in organic structures. The contact electrodes continue to play a significant role in controlling device performance. The deposition of metals as one contact and the use of ITO as the transparent conducting electrode are limiting factors. New strategies are needed to develop transparent conductors and substrates that take into account their “end use” in organic-based solar energy conversion devices. This problem can be addressed by focusing on the interface with the existing transparent oxides or by developing new molecule-based conductors that provide better compatibility. SCIENTIFIC CHALLENGES Key scientific challenges that must be overcome include optimizing the target molecular, polymeric, and nanocrystalline structures to produce systems that will provide extraction of energy over the full range of the solar spectrum, including the challenging near-infrared region. There is also a need to understand the relationship between electronic structure and excited state properties of the constituent species of these new systems and to understand how this relationship is affected through their interactions with each other. The development and understanding of structures that can exhibit efficient frequency up-conversion and downconversion for advanced, third-generation device structures will also benefit from such a fundamental understanding. Factors that control the processes that occur at the interfaces between dissimilar phases pose an additional challenge that must also be addressed. This includes the interface within the components of the active photoconversion medium, at the interface between stacked junctions of a tandem design and at the interface with the external contacts. The challenge is to understand how to manipulate and enhance the transport of excitons to the interface, where they can be dissociated and the resulting charge carriers transported away, while inhibiting any recombination processes. POTENTIAL IMPACT The potential impact of success in the development of new organic photovoltaic systems and device structures will be high-performance, light-weight, conformable, photovoltaic solar arrays that contain sustainable and nontoxic species. REFERENCES C.J. Brabec, “Organic Photovoltaics: Technology and Market,” Sol. Energy Mater. Sol. Cells 83, 273–292 (2004). 106
W.U. Huynh, X. Peng, and P. Alivisatos, “CdSe Nanocrystal Rods/Poly(3-hexylthiophene) Composite Photovoltaic Devices,” Adv. Mater. 11, 923–927 (1999). F. Padinger, R.S. Rittberger, and N.S. Sariciftci, “Effects of Postproduction Treatment on Plastic Solar Cells,” Advanced Functional Materials 13, 18 (2003). P. Peumans and S.R. Forrest, “Very-high-efficiency Double Heterostructure Copper Phthalocyanine/C60 Photovoltaic Cells,” Appl. Phys. Lett. 79, 126–128 (2001). B.Q. Sun, H.J. Snaith, A.S. Dhoot, S. Westenoff, and N.C. Greenham, “Vertically Segregated Hybrid Blends for Photovoltaic Devices with Improved Efficiency,” J. Appl. Phys. 97 (2005). M.M. Wienk et al., “Efficient Methano[70]fullerene/MDMO-PPV Bulk Heterojunction Photovoltaic Cells,” Angew. Chem., Int. Ed. 42, 3371–3375 (2003). 107
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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
Page 69: J. Seth, V. Palaniappan, R.W. Wagne
Page 72 and 73: THREE TYPES OF CONCENTRATED SOLAR
Page 74 and 75: Solar Thermal to Electric Energy Co
Page 76 and 77: Tm = mean temperature Z = measure o
Page 78 and 79: control and further diode developme
Page 80 and 81: An overview of solar thermochemical
Page 82 and 83: for electron and phonon band struct
Page 84 and 85: coefficient. The thermal conductivi
Page 86 and 87: J.J. Greffet, R. Carminati, K. Joul
Page 89 and 90: CROSS-CUTTING RESEARCH CHALLENGES B
Page 91 and 92: ange of time and length scales span
Page 93 and 94: Research Issues Advances in the syn
Page 95 and 96: Advances across several science fro
Page 97 and 98: Figure 19 Transparent conductive el
Page 99 and 100: Carrier generation, relaxation, and
Page 101 and 102: E. Hutter and J.H. Fendler, “Expl
Page 103: PRIORITY RESEARCH DIRECTIONS Revolu
Page 106 and 107: RESEARCH DIRECTIONS Several paths e
Page 108 and 109: Multiple Energy Level Solar Cells I
Page 110 and 111: Strain Relaxation. Growth of layers
Page 112 and 113: the relevant elastic and inelastic
Page 114 and 115: A.J. Nozik, “Quantum Dot Solar Ce
Page 116 and 117: these new organic structures, and t
Page 118 and 119: Figure 30 Schematic diagram (right)
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Page 124 and 125: Figure 32 One important example of
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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
Page 146 and 147: coupling in multi-cofactor-containi
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Page 150 and 151: low toxicity, and processibility. T
Page 152 and 153: 8 electrons) are extremely limited.
Page 154 and 155: largely unknown are the fundamental
Page 156 and 157: nanostructure design, and developme
Page 158 and 159: ealize an efficient artificial phot
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
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The continued advances in energy- a
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for the detailed understanding and
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160
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A shortcoming of this approach is t
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of ~2.4 at 300K and quantum-dot PbT
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High-throughput Experimental Screen
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Solar Concentrators and Hot Water H
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G. Chen, M.S. Dresselhaus, J.-P. Fl
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Materials and Processing Methods to
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materials and fabrication approache
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multi-electron H2O and CO2 activati
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178
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180
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and quantum dots. Quantum dots are
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184
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186
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Flux (mA/eV.cm2 Flux (mA/eV.cm ) 2
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Table 1 Worldwide PV Module Product
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Amorphous Silicon. From its discove
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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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230
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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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