Organic Photovoltaics: Mechanisms, Materials, and Devices

by Sun; Sam-Shajing

• ISBN13: 9780824759636
• ISBN10: 082475963X
• Edition: 1st
• Format: Hardcover
• Copyright: 2005-03-29
• Publisher: CRC Press

Summary

Recently developed organic photovoltaics (OPVs) show distinct advantages over their inorganic counterparts due to their lighter weight, flexible shape, versatile materials synthesis and device fabrication schemes, and low cost in large-scale industrial production. Although many books currently exist on general concepts of PV and inorganic PV materials and devices, few are available that offer a comprehensive overview of recently fast developing organic and polymeric PV materials and devices. Organic Photovoltaics: Mechanisms, Materials, and Devicesfills this gap. The book provides an international perspective on the latest research in this rapidly expanding field with contributions from top experts around the world. It presents a unified approach comprising three sections: General Overviews; Mechanisms and Modeling; and Materials and Devices. Discussions include sunlight capture, exciton diffusion and dissociation, interface properties, charge recombination and migration, and a variety of currently developing OPV materials/devices. The book also includes two forewords: one by Nobel Laureate Dr. Alan J. Heeger, and the other by Drs. Aloysius Hepp and Sheila Bailey of NASA Glenn Research Center. Organic Photovoltaicsequips students, researchers, and engineers with knowledge of the mechanisms, materials, devices, and applications of OPVs necessary to develop cheaper, lighter, and cleaner renewable energy throughout the coming decades.

Table of Contents

Section 1: General Overviews
The Story of Solar Cells	3	(16)
John Perlin
The First Solid-State Solar Cell	3	(1)
The Discovery of the Silicon Solar Cell	4	(1)
The First Practical Application of Silicon Solar Cells	4	(1)
Terrestrial Applications	5	(11)
The Future of Photovoltaics	16	(3)
References	17	(2)
Inorganic Photovoltaic Materials and Devices: Past, Present, and Future	19	(18)
Aloysius F. Hepp
Sheila G. Bailey
Ryne P. Raffaelle
Introduction	20	(2)
Recent Aspects of Advanced Inorganic Materials	20	(1)
Focus: Advanced Materials and Processing	20	(1)
Increased Efficiency	21	(1)
Increased Specific Power	21	(1)
Overview of Specific Materials	22	(3)
High-Efficiency Silicon	22	(1)
Polycrystalline Silicon	22	(1)
Amorphous Silicon	22	(1)
Gallium Arsenide and Related III--V Materials	23	(1)
Thin-Film Materials	24	(1)
Advanced Concepts	25	(7)
Multijunction III--V Devices	25	(2)
Nanotechnology---Specifically Quantum Dots	27	(1)
Advanced Processing for Low-Temperature Substrates	27	(2)
Concentrator Cells	29	(1)
Integrated Power Devices	30	(2)
Applications	32	(1)
Terrestrial	32	(1)
Aerospace	32	(1)
Summary and Conclusions	33	(4)
References	34	(3)
Natural Organic Photosynthetic Solar Energy Transduction	37	(12)
Robert E. Blankenship
Introduction	38	(1)
Photosynthesis is a Solar Energy Storage Process	38	(1)
Where Photosynthesis Takes Place	39	(1)
Photosynthetic Pigments	39	(2)
The Four Phases of Energy Storage in Photosynthetic Organisms	41	(1)
Antennas and Energy Transfer Processes	41	(3)
Primary Electron Transfer in Reaction Centers	44	(3)
Stabilization by Secondary Reactions	47	(1)
Conclusions	47	(2)
References	48	(1)
Solid-State Organic Photovoltaics: A Review of Molecular and Polymeric Devices	49	(58)
Paul A. Lane
Zakya H. Kafafi
Introduction	50	(3)
Overview	50	(1)
Device Characterization	50	(3)
Molecular OPVs	53	(13)
Organic Heterojunction Solar Cells	53	(3)
Molecular OPVs with Bulk Heterojunctions	56	(4)
High-Efficiency Molecular OPVs with Exciton Blocking Layers	60	(4)
Open-Circuit Voltage and Tandem Solar Cells	64	(2)
Polymer OPVs	66	(19)
Single-Layer Polymer Devices	66	(2)
Polymer Dye Solar Cells	68	(8)
Polymer Blend and Multilayer Solar Cells	76	(9)
Hybrid OPVs	85	(11)
Polymer--Quantum Dot Devices	85	(4)
Polymer--Sensitized TiO2	89	(5)
Solid State Dye-Sensitized Solar Cells	94	(2)
Concluding Remarks	96	(11)
References	97	(10)
Section 2: Mechanisms and Modeling
Simulations of Optical Processes in Organic Photovoltaic Devices	107	(32)
Nils-Krister Persson
Olle Ingands
Introduction	108	(2)
The Seven Processes of Polymer Photovoltaic Devices	110	(3)
Incoupling of the Photon	110	(1)
Photon Absorption	111	(1)
Exciton Formation	111	(1)
Exciton Migration	112	(1)
Exciton Dissociation	112	(1)
Charge Transport	112	(1)
Charge Collection	113	(1)
Routes to Optical Models of PPVDs	113	(1)
The Matrix Model	114	(9)
General Assumptions	114	(1)
Derivation --- the Stack Model	115	(5)
Taking Into Account the Substrate	120	(2)
Solar Spectrum	122	(1)
Efficiencies	122	(1)
Simulations and Results	123	(12)
Simulation of the Optical Electric Field Inside the Device	127	(1)
Q-Profile for Different Wavelengths	127	(1)
Q-Profile for Different Thicknesses, Monochromatic Illumination	128	(1)
Polychromatic Q-Profile	128	(2)
Device Optimization	130	(1)
Optimizing the Double Layer Structure	130	(1)
Optimizing the Blend Layer Structure	131	(2)
Sensitivity Analysis	133	(1)
Quantum Efficiency	133	(1)
Optical Power Efficiency	133	(1)
Energy Redistribution	134	(1)
Summary	135	(4)
References	136	(3)
Coulomb Forces in Excitonic Solar Cells	139	(22)
Brian A. Gregg
The Essence of Excitonic Solar Cells	140	(2)
Differences Between Conventional and Excitonic Semiconductors	140	(1)
Characteristics of Excitonic Semiconductors	141	(1)
Charge Carrier Photogeneration in CSCs and XSCs	142	(3)
Forces and Fluxes in XSCs	143	(1)
The Chemical Potential Energy Gradient in XSCs	144	(1)
Open Circuit Photovoltage	145	(1)
Doping OSCs	145	(6)
Adventitiously Doped π-Conjugated Polymers	146	(1)
Purposely Doped Perylene Diimide Films	146	(1)
Superlinear Increase in Conductivity with Doping Density	147	(3)
No Shallow Dopants in XSCs	150	(1)
Carrier Transport in XSCs	151	(6)
The nμ Product	151	(1)
Adventitiously Doped XSCs	151	(1)
The Poole--Frenkel Mechanism	152	(2)
Space Charge Limited Currents	154	(2)
Field-Dependent Carrier Mobilities	156	(1)
Summary	157	(4)
Acknowledgment	158	(1)
References	158	(3)
Electronic Structure of Organic Photovoltaic Materials: Modeling of Exciton-Dissociation and Charge-Recombination Processes	161	(22)
Jerome Cornil
Vincent Lemaur
Michelle C. Steel
Helene Dupin
Annick Burquel
David Beljonne
Jean-Luc Bredas
Introduction	162	(1)
The Failure of the Static View	163	(2)
Theoretical Approach	165	(4)
Dynamical Aspects	169	(4)
Strategies for Efficient Charge Generation	173	(5)
Specifically Designed Supramolecular Architectures	173	(1)
Donor Bridge Acceptor Architectures	174	(1)
Symmetry Effects	175	(2)
Low-Bandgap Polymers	177	(1)
Triplet Excitons	178	(1)
Conclusions	178	(5)
Acknowledgments	178	(1)
References	179	(4)
Optimization of Organic Solar Cells in Both Space and Energy--Time Domains	183	(34)
Sam-Shajing Sun
Carl E. Bonner
Introduction	184	(1)
Fundamentals and Current Problems of Organic Photovoltaics	185	(6)
Photon Absorption and Exciton Generation	188	(1)
Exciton Diffusion	189	(1)
Exciton Separation and Charge Carrier Generation	189	(1)
Carrier Diffusion to the Electrodes	189	(1)
Carrier Collection at the Electrodes	190	(1)
Optimization in the Spatial Domain Via A --DBAB- Type Block Copolymer	191	(12)
Block Copolymers and Self-Assembled Supramolecular Nanostructures	191	(1)
Design and Development of a --DBAB- Type Block Copolymer for a ``Tertiary'' Supramolecular Nanostructure	192	(4)
Materials and Equipment, Experimental	196	(2)
Results and Discussion on Spatial Domain Optimization	198	(5)
Optimization in the Energy--Time Domain	203	(8)
Background	203	(1)
Formulation	204	(2)
Results and Discussion	206	(5)
Conclusions and Future Perspectives	211	(6)
Acknowledgments	212	(1)
References	212	(5)
Section 3: Materials and Devices
Bulk Heterojunction Solar Cells	217	(22)
Harald Hoppe
Niyazi Serdar Sariciftci
Introduction	217	(1)
Photoinduced Electron Transfer from Conjugated Polymers onto Fullerenes	218	(2)
The Bulk Heterojunction Concept	220	(3)
Metal-Insulator--Metal (MIM) Picture	223	(2)
Bilayer Heterojunction Devices	225	(1)
Bulk Heterojunction Devices	226	(2)
The Open Circuit Potential, VOC	228	(3)
Double Cable Polymers	231	(1)
Outlook	232	(7)
References	232	(7)
Organic Solar Cells Incorporating a p--i--n Junction and a p--n Homojunction	239	(32)
Masahiro Hiramoto
Introduction	240	(1)
p--i--n Junction Cells	241	(11)
Motivation	241	(1)
Direct Heteromolecular Contact as a Photocarrier Generation Site	241	(3)
Three-Layered Cells	244	(2)
p--i--n Energy Structure	246	(3)
Application of Inorganic Semiconductors to the n-Type Layer	249	(1)
Sensitization Mechanism of Photocarrier Generation at Heteromolecular Contacts	250	(2)
Control of the Nanostructure of Co-Deposited Films	252	(7)
Motivation	252	(1)
Photovoltaic Properties vs. Substrate Temperature	252	(1)
Nanostructure vs. Substrate Temperature	253	(2)
Photocurrent Generation in Co-Deposited Films	255	(1)
Three-Layered Cells Incorporating Crystalline--Amorphous Nanocomposite Films	256	(3)
Nanostructure Design	259	(1)
p--n Homojunction Cells	259	(9)
Motivation	259	(1)
Efficient Purification by Reactive Sublimation	260	(2)
pn-Control of a Single Organic Semiconductor by Doping	262	(4)
p--n Homojunction in Perylene Pigment Film	266	(2)
p--n Control Technique	268	(1)
Conclusion	268	(3)
Acknowledgment	269	(1)
References	269	(2)
Liquid-Crystal Approaches to Organic Photovoltaics	271	(28)
Bernard Kippelen
Seunghyup Yoo
Joshua A. Haddock
Benoit Domercq
Stephen Barlow
Britt Minch
Wei Xia
Seth R. Marder
Neal R. Armstrong
Introduction	272	(2)
Modeling of Solar Cells	274	(2)
Transport in Organic Semiconductors	276	(6)
Disorder Formalism for Transport in Amorphous Materials	277	(1)
Mobility Measurement Techniques	278	(4)
Semiconducting Liquid Crystals	282	(8)
Fundamentals of Liquid Crystals	282	(2)
Transport in Liquid Crystals	284	(1)
Calamitic Materials	284	(2)
Discotic Materials	286	(3)
Supramolecular Architectures	289	(1)
Overview of Liquid-Crystal-Based Photovoltaic Cells	290	(3)
Conclusion	293	(6)
Acknowledgments	294	(1)
References	294	(5)
Photovoltaic Cells Based on Nanoporous Titania Films Filled with Conjugated Polymers	299	(14)
Kevin M. Coakley
Michael D. McGehee
Introduction	299	(2)
Nanoporous Titania Films	301	(1)
Filling Nanopores with Conjugated Polymers	302	(3)
Performance of Photovoltaic Cells and Characterization of Polymer--Titania Films	305	(4)
Photovoltaic Cells with Non-Interpenetrating Semiconductors	305	(2)
Interpenetrating Polymer--Titania Nanostructures	307	(2)
Future Outlook	309	(4)
References	310	(3)
Solar Cells Based on Cyanine and Polymethine Dyes	313	(18)
He Tian
Fanshun Meng
Introduction	314	(1)
Cyanine and Polymethine Dye Sensitization	314	(10)
Cyanine Dyes	314	(3)
Hemicyanine Dyes	317	(3)
Merocyanine Dyes	320	(1)
Other Polymethine Dyes	321	(3)
Thin Film Heterojunction Photovoltaic Devices	324	(1)
Future Prospects	325	(6)
Acknowledgments	327	(1)
References	327	(4)
Semiconductor Quantum Dot Based Nanocomposite Solar Cells	331	(20)
Marvin H. Wu
Akira Ueda
Richard Mu
Introduction	332	(3)
Quantum Dot--Organic Polymer Composite Solar Cells	335	(6)
Published Results	336	(1)
Power Conversion in Quantum Dot--Polymer Composite Solar Cells	337	(1)
Light Absorption and Generation of Charge Carriers	337	(1)
Separation and Extraction of Carriers from Quantum Dots	338	(2)
Carrier Transport	340	(1)
Conclusions	341	(1)
Quantum Dot Sensitized Photoelectrochemical Solar Cells	341	(4)
Introduction	341	(2)
Issues Concerning Materials Used as QDSSCs	343	(1)
Challenges in Materials and Device Development	344	(1)
Conclusion	345	(6)
Acknowledgments	346	(1)
References	346	(5)
Solar Cells Based on Composites of Donor Conjugated Polymers and Carbon Nanotubes	351	(16)
Emmanuel Kymakis
Gehan A. J. Amaratunga
Introduction	352	(4)
Absorption Spectroscopy	356	(1)
Current Voltage Characteristics	356	(5)
Light Intensity Dependence Measurements	358	(2)
Open Circuit Voltage	360	(1)
Nanotube Concentration Dependence	361	(2)
Future Directions	363	(1)
Conclusions	364	(3)
References	364	(3)
Photovoltaic Devices Based on Polythiophene/C60	367	(20)
L. S. Roman
Introduction	368	(1)
Organic Photovoltaic Devices	368	(3)
Bilayers of Polythiophenes/C60	371	(7)
Optical Modeling of PEOPT/C60 Devices	372	(2)
Electrical Transport in PEOPT/C60 Diodes in Dark	374	(2)
Electrical Transport in PEOPT/C60 Photodiodes under Illumination	376	(2)
Blends of Polythiophenes/C60	378	(5)
Conclusions	383	(4)
Acknowledgments	384	(1)
References	384	(3)
Alternating Fluorene Copolymer--Fullerene Blend Solar Cells	387	(16)
Olle Ingands
Fengling Zhang
Xiangjun Wang
Abay Gadisa
Nils-Krister Persson
Mattias Svensson
Erik Perzon
Wendimagegn Mammo
Mats R. Andersson
Introduction	387	(3)
Alternating Polyfluorene Copolymers: Synthesis and Characterization	390	(1)
Chemical Synthesis	390	(1)
Alternating Polyfluorene Copolymers: Electronic Structure and Optical Absorption	391	(2)
Optical Transitions and Electronic Structure	392	(1)
Dielectric Functions of APFO Films	393	(1)
Photoluminescence Processes in APFO materials	393	(1)
Electronic Transport in APFOs	393	(2)
Polyfluorene--Fullerene Blends: Morphology and Optical Properties	395	(2)
Polyfluorene--Fullerene Blends in Devices: Performance	397	(3)
Temperature Dependence of Photovoltaic Device Performance	398	(2)
Summary	400	(3)
Acknowledgments	400	(1)
References	400	(3)
Solar Cells Based on Diblock Copolymers: A PPV Donor Block and a Fullerene Derivatized Acceptor Block	403	(18)
Rachel A. Segalman
Cyril Brochon
Georges Hadziioannou
Introduction	404	(3)
Microphase Separation of Block Copolymers	405	(2)
Block Copolymers for Photovoltaic Applications	407	(1)
Synthesis of PPV-Based Donor--Acceptor Diblock Copolymer	407	(4)
Synthesis of Diblock Rod--Coil Copolymers: General Aspects	407	(1)
Synthesis of PPV Macroinitiator	408	(1)
Polymerization with the PPV Macroinitiator and Functionalization of the Coil Block	409	(2)
Phase Behavior of the PPV-Based Diblock Copolymers	411	(4)
Aggregation of PPV-b-PS Diblock Copolymers in Solution	412	(1)
Self Organization of PPV-based Block Copolymers in Thin Films	413	(2)
Photovoltaic Response of the Donor--Acceptor Block Copolymer	415	(2)
Conclusions and Outlook	417	(4)
References	418	(3)
Interface Electronic Structure and Organic Photovoltaic Devices	421	(32)
Yongli Gao
Introduction	422	(2)
Symmetry of Metal--Organic Interfaces: Pentacene with Au. Ag, and Ca	424	(3)
Mechanisms of Interface Dipole Formation	427	(2)
Doping and Energy Level Shift: Cs in CuPc	429	(3)
Interface Engineering in OSCs: LiF	432	(3)
ITO Surface Treatment and its Interface with Organic: NPB/ITO	435	(4)
Organic--Organic Interface: NPB and Alq3	439	(4)
Dynamics of Interface Charge Transfer: TPD and DPEP	443	(5)
Final Remarks	448	(5)
Acknowledgments	448	(1)
References	449	(4)
The Influence of the Electrode Choice on the Performance of Organic Solar Cells	453	(26)
Aleksandra B. Djurisic
Chung Yin Kwong
Introduction	454	(1)
Criteria for Electrode Choice	455	(3)
Schottky Barrier Solar Cells	456	(1)
Heterojunction Solar Cells	456	(1)
Dye-Sensitized Solar Cells	457	(1)
Commonly Used Anodes	458	(11)
Indium Tin Oxide	459	(9)
Poly(Ethylene Dioxythiophene): Polystyrene Sulfonic Acid (PEDOT:PSS)/ITO	468	(1)
Polyaniline/ITO and Self-Assembled Monolayers on ITO	468	(1)
Semitransparent Metals	469	(1)
Commonly Used Cathodes	469	(2)
Single Layer Metal Cathode	469	(1)
LiF/Aluminum	470	(1)
BCP/Ag and BCP/A1	470	(1)
Conclusions	471	(8)
References	472	(7)
Conducting and Transparent Polymer Electrodes	479	(16)
Fengling Zhang
Olle Inganas
Introduction	480	(1)
Properties of PEDOT--PSS	481	(4)
Conductivity of PEDOT--PSS	482	(1)
The Optical Properties of PEDOT--PSS Film	482	(1)
Processing and Patterning	483	(2)
Work Function	485	(1)
Application in PVDs	485	(5)
PEDOT--PSS Used as a Buffer Layer	485	(1)
Increase the Rectification and Photovoltage of Polymer PVDs	485	(1)
Tuning the Photovoltage of Polymer PVDs	486	(2)
PEDOT--PSS as an Electrode in Polymer PVDs	488	(2)
Outlook	490	(5)
Acknowledgment	490	(1)
References	491	(4)
Progress in Optically Transparent Conducting Polymers	495	(34)
Venkataramanan Seshadri
Gregory A. Sotzing
Introduction	496	(1)
Towards Transparent ICPs	497	(25)
Polymers with Electron-Rich Moieties	497	(6)
Polymers Containing Electron-Withdrawing Repeat Units	503	(2)
Fused Aromatics as Repeat Units	505	(6)
Arylvinylenes and Arylmethines	511	(4)
Donor--Acceptor Type Polymers	515	(7)
Conclusions	522	(7)
References	523	(6)
Optoelectronic Properties of Conjugated Polymer/Fullerene Binary Pairs with Variety of LUMO Level Differences	529	(30)
Steffi Sensfuss
Maher Al-Ibrahim
Introduction	530	(3)
Optoelectronic Properties of Donor--Acceptor Materials and Their Influence on the Photovoltaic Parameters	533	(21)
Fullerene and Fullerene Derivatives as Electron Acceptors	533	(1)
Regioregular P3ATs as Electron Donors	533	(1)
Electrochemical Properties of Poly(3-alkylthiophene)s	534	(1)
Optical Properties of Poly(3-alkylthiophene)s	535	(1)
Photoinduced Electron Transfer in P3AT/Fullerene Systems	535	(4)
Photovoltaic Devices Based on P3ATs/PCBM	539	(3)
Summary of P3ATs/Fullerene Systems	542	(1)
MDMO-PPV, DE69, and DE21 as Electron Donors	543	(1)
Electrochemical Properties of MDMO-PPV, DE69, and DE21	543	(1)
Optical Properties of MDMO-PPV, DE69, and DE21	544	(1)
Photoinduced Electron Transfer in MDMO-PPV, DE69, or DE21--Fullerene Systems	545	(6)
Photovoltaic Devices Based on MDMO-PPV/PCBM, DE69/PCBM, and DE21/PCBM	551	(2)
Summary of MDMO-PPV/PCBM and PPE-PPV/PCBM Systems	553	(1)
Conclusions	554	(5)
Acknowledgments	554	(1)
References	554	(5)
Polymer-Fullerene Concentration Gradient Photovoltaic Devices by Thermally Controlled Interdiffusion	559	(20)
Martin Drees
Richey M. Davis
Randy Heflin
Introduction	560	(1)
Experimental	561	(1)
MEH-PPV/C60 Devices	561	(11)
Thermally Controlled Interdiffusion	562	(4)
Dependence on MEH-PPV Thickness	566	(3)
In situ Observation of Interdiffusion	569	(1)
Morphology of the Interdiffused Devices	570	(2)
P3OT/C60 Devices	572	(3)
Summary	575	(4)
Acknowledgments	576	(1)
References	577	(2)
Vertically Aligned Carbon Nanotubes for Organic Photovoltaic Devices	579	(20)
Michael H.-C. Jin
Liming Dai
Introduction	580	(3)
Polymer/Carbon Nanotube Solar Cells	583	(3)
Vertically Aligned Carbon Nanotubes for Optoelectronic Applications	586	(4)
Nano-Engineering for the Future	590	(2)
Conclusion	592	(7)
Acknowledgments	593	(1)
References	593	(6)
Index	599