Optoelectronics and. Colloidal Quantum Dot. Photovoltaics. Cambridge GERASIMOS KONSTANTATOS EDWARD H. SARGENT. University of Toronto.

Transcription

1 Colloidal Quantum Dot Optoelectronics and Photovoltaics Edited by GERASIMOS KONSTANTATOS ICFO The Institute of Photonic Sciences, Barcelona EDWARD H. SARGENT University of Toronto Cambridge UNIVERSITY PRESS

2 Contents List of contributors Preface page xi xiii 1 Engineering colloidal quantum dots: synthesis, surface chemistry, and selfassembly Maryna I. Bodnarchuk and Maksym V. Kovalenko l l.1 Colloidal synthesis of inorganic nanocrystals and quantum dots Introductory remarks: history and terminology Basics of the surfactantassisted colloidal synthesis of NC quantum dots Longrange ordered NC solids Singlecomponent NC superlattices Multicomponent NC superlattices Shapedirected selfassembly of NCs Surface chemistry a gateway to applications of NCs Organic capping ligands Complete removal of organic ligands and inorganic surface functionalization 19 References 20 2 Aqueous based colloidal quantum dots for optoelectronics 30 Vladimir Lesnyak and Nikolai Gaponik 2.1 Introduction Aqueous colloidal synthesis of semiconductor NCs ZnXNCs Alloyed ZnSe based NCs CdXNCs Core/shell CdTe based NCs Alloyed CdTe based NCs CdSe, CdSe/CdS NCs HgX and PbX NCs 39

3 vi Contents HgXNCs PbXNCs Assemblies and functional architectures of NCs LbL assembly technique Assembly of NCs on micro and nanobeads Covalent coupling of NCs Controllable aggregation Nanowires and nanosheets Nanocrystal based gels and aerogels Conclusions and outlook 50 References 51 3 Electronic structure and optical transitions in colloidal semiconductor nanocrystals 59 Todd D. Krauss and Jeffrey J. Peterson 3.1 Introduction Foundational concepts A simple model Experimental evidence for quantum confinement Engineered quantum dot structures Advanced theoretical treatments Atomistic approaches Current challenges and future outlook 80 References 81 4 Charge and energy transfer in polymer/nanocrystal blends: physics and devices 87 Kevin M. Noone and David S. Ginger 4.1 Introduction A brief history of QD/polymer optoelectronics Quantum dot light emitting diodes (QDLEDs) sizetunable emission across the spectrum Quantum dot photovoltaics (QDPV) and photodetectors converting photons to electrons QDPVs Quantum dot photodetectors The QDorganic interface ligands and more Ligands Energetics Charge transfer and Forster resonance energy transfer (FRET) in QDLEDs Type II heterojunctions and charge transfer in QDPVs Conclusion and future outlook 104 References 105

4 Contents vii 5 Multiple exciton generation in semiconductor quantum dots and electronically coupled quantum dot arrays for application to thirdgeneration photovoltaic solar cells 112 Matthew C. Beard, Joey M. Luther, and Arthur J. Nozik 5.1 Introduction Relaxation dynamics of photogenerated electronhole pairs in QDs Transient absorption spectroscopy (TA) Multiple exciton generation (MEG) MEG in QDs MEG controversy and role of photocharging MEG efficiency and comparison to impact ionization in bulk semiconductors QD solar cells MEG photocurrent and determination of the internal quantum efficiency (IQE) in QD solar cells QD arrays MEG in PbSe QD arrays Conclusions 140 References Colloidal quantum dot light emitting devices 148 Vanessa Wood, Matthew Panzer, SethCoe Sullivan, and Vladimir Bulovic 6.1 Introduction Why QDs for LEDs? Saturated colors Solution processable Stability QD and device physics influencing LED performance Quantifying the luminescence efficiency QD surface states QD charging Charge transport in QD films Field driven luminescence quenching Isolating the effects of charge and field Characterizing QDLEDs QDLEDs based on optical downconversion QDLEDs based on organic charge transport layers Deposition of QDs: spin casting, phase separation, and microcontact printing Operation of colloidal QDLEDs QDLEDs with inorganic charge transport layers Reasons for inorganic charge transport layers 165

5 viii Contents Fabrication of all inorganic QDLEDs Operation of QDLED with inorganic charge transport layers Improving the efficiency of QDLEDs with inorganic charge transport layers Future work 167 References Colloidal quantum dot photodetectors 173 Gerasimos Konstantatos 7.1 Introduction Applications of topsurface photodetectors Colloidal quantum dots (CQDs) for light detection Fundamentals of photodetectors Types of photodetectors Figures of merit Prior art in solutionprocessed photodetectors Solutionprocessed QD photoconductors Photoconductive gain and noise in PbS QD photodetectors Visiblewavelength and multispectral photodetection Control of temporal response in photoconductive detectors via trap state engineering CQD based phototransistors CQD photodiodes Conclusions summary 193 References Optical gain and lasing in colloidal quantum dots 199 Sjoerd Hoogland 8.1 Introduction Optical properties of colloidal nanocrystal quantum dots Carrier dynamics in colloidal quantum dots Auger recombination Poisson statistics and state filling Gain in solid state nanocrystal quantum dot films Amplified spontaneous emission (ASE) Variable strip length (VSL) for optical gain measurements Experimental techniques for waveguide loss measurement in colloidal quantum dot films Modal gain in visible colloidal quantum dots based on cadmium chalcogenides Modal gain in infrared colloidal quantum dots based on lead chalcogenides 213

6 Contents ix 8.5 Spectral and temporal characteristics of optical gain in nanocrystal quantum dots Visible colloidal quantum dots based on cadmium chalcogenides Infrared colloidal quantum dots based on lead chalcogenides Colloidal nanocrystal lasers Microcapillary Microsphere resonators 223 resonators Distributed feedback resonators Microtoroid resonators Other resonators Future prospects Single exciton gain 226 References Heterojunction solar cells based on colloidal quantum dots 233 Jeffrey J. Urban and Delia J. Milliron 9.1 Introduction Chemistry of CQDs for solar cells Physics of CQDs for solar cells Electronic structure evolution in low dimensional systems Fundamentals of lightmatter interactions in QDs Selection rules and the complications of// Optical and electronic properties of CQD films for solar cells Device physics and design of CQD heterojunction solar cells Technology and scientific outlook 250 References Solutionprocessed infrared quantum dot solar cells 256 Jiang Tang and Edward H. Sargent 10.1 Introduction Infrared CQDs for the full absorption of solar spectrum Bandgap engineering for the broadband solar spectrum match Light absorption in CQD film Semiconductor solar cell fundamentals Fundamentals of pn junction Fundamentals of solar cells Implications for CQD solar cell optimization Electrical properties of CQD films Measurements of electrical properties of CQD films Transport in CQD film CQD passivation CQD film doping Dielectric constant of CQD film 276

7 X Contents 10.5 Progress in CQD solar cell performance Schottky solar cells Heterojunction solar cells Device stability Perspectives and conclusions 285 References Semiconductor quantum dot sensitized Ti02 mesoporous solar cells 292 Lioz Etgar, Hyo Joong Lee, Sang II Seok, Md. K. Nazeeruddin, and Michael Gratzel 11.1 Introduction Mesoscopic PbS quantum dot/tioo heterojunction solar cells Solidstate PbS/Ti02 heterojunction solar cell QD/TiCb mesoporous solar cell using the SILAR process Cobalt complexbased redox couples in CQDTiCh mesoporous solar cells 305 References 308 Index 310