Handbook of Transparent Conductors

534 Pages·11.938 MB·English

by  Ginley D.S., Hosono H., Paine D.C. (Eds.)

David S. Ginley
Editor
Hideo Hosono David C. Paine
l
Associate Editors
Handbook of Transparent
Conductors
Editor
Dr.DavidS.Ginley
NREL
Photovoltaics&ElectronicMaterials
Center&BasicSciencesCtr.
ColeBlvd.1617
80401-3393GoldenColorado
USA
[email protected]
AssociateEditors
Dr.HideoHosono Prof.DavidC.Paine
TokyoInstituteofTechnology BrownUniversity
Materials&StructuresLab. DivisionEngineering
Nagatsuta4259 610Barus&Holley
226-8503Yokohama HopeStreet182
Midori-ku 02912ProvidenceRhodeIsland
Japan USA
[email protected] [email protected]
ISBN978-1-4419-1637-2 e-ISBN978-1-4419-1638-9
DOI10.1007/978-1-4419-1638-9
SpringerNewYorkHeidelbergDordrechtLondon
LibraryofCongressControlNumber:2010935196
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Preface
TransparentConductingOxides(TCOs)areauniqueclassofmaterialsthatexhibit
both transparency and electronic conductivity simultaneously. These materials
havefoundwidespreaduseindisplays,photovoltaics,low-ewindows,andflexible
electronics.Inmanyoftheseapplications,theTCO’s,areenablingintheirroleas
transparent contacts. However,increasingly, the demands required extend beyond
the combination of conductivity and transparency, where indeed higher perfor-
mance is needed, but now include work function, morphology, processing and
patterningrequirements, long term stability, lower cost and elemental abundance/
green materials. As these needs have begun to emerge over the last 5 years they
havestimulatedadramaticresurgenceofresearchinthefieldleadingtomanynew
materials and processes. Overall it is the purpose of this book to provide both a
snapshotofthenewandenablingworkinthefieldandtoprovidesomeindications
of what might be coming next. We note that now the field of Transparent Con-
ductors (TC’s) includes not only conventional TCOs but also metal and carbon
nano-composites, grapheme and polymer based TC materials. While the book
primarilyfocusesontheTCOssomecomparisonsaremadetothenewermaterials.
Todothiswehaveassembledagroupofauthorsrepresentingmostoftheleading
groupsinthefield.
Historically,TCOswerelimitedprimarilytotinoxidewithfluorinedoping,zinc
oxide with aluminum doping and Indium tin oxide. Over the past 5–10 years the
fieldhasexplodedtoincludeavastlyincreasednumberofn-typematerialsandto
add in a class of new p-type materials. In addition, the historically held view that
crystallinematerialshavesuperiorproperties,hasbeenchallengedbyanemergence
of new amorphous TCOs that have properties as good as or better than their
crystallinecounterparts.Thesematerialshaveledtothedevelopmentofamorphous
oxidetransistorswhichoffertheadvantageoflowtemperatureprocessingandthe
promise of flexible electronics on polymer substrates. In their role as a channel
material in thin film transistor structures, TCO’s with controlled carrier densities
areoftentermedtransparentoxidesemiconductors(TOS)sincetheirkeyproperties
v
vi Preface
may lie in the limited to non-conductive regime. To capture this diversity of
materials,processingandapplications,wehaveorganizedthebookasfollows.
Chapter1introducesTCOsandcoversthehistoricmaterialsandtheirproperties
and uses this background to put some of the newly emergent materials into a
technologicalcontext.Chapter2presentsadetaileddiscussionofthebasicelectronic
structures ofTCO materials emphasizing thekeyproperties whichgive them their
uniqueproperties.Chapter3thenprovidesanoverviewofmethodsforthemeasure-
ment andinterpretation of transport properties in TCOs based of the Drude model
with a focus on the method of four coefficients for the determination of critical
parameters such as carrier type, mobility and scattering mechanisms in multinary
oxides.Chapter4coversthebasicphysicsof,andpracticaltoolsfor,thecharacteri-
zationofimportantTCOparametersincludingatomicstructure,opticalproperties,
electricaltransport,workfunctionandotherpropertiesthatmustbebetterunderstood
asTCO’sbecomeusedinnovelapplicationssuchasthinfilmtransistors.Chapter5
presentsapictureofthecurrentInbasedTCOscoveringboththetraditionalInSnO
x
materialswhichhavebeenthegoldstandardofTCOsandtheemergingamorphous
materials. Chapter 6 presents an overview of the tin oxide based TCO materials.
While historically thesematerialshavebeen producedinexceptionallylargeareas
newworkhasbeguntoimprovetheirproperties.Chapter7reviewsthestateoftheart
forZnO.Thismaterial,duetoitsnaturalabundanceandtheeasewithwhichitcanbe
depositedviabothphysicalandchemicalroutes,hasimportantapplicationsbothasa
traditional transparent contact and great potential as an active optoelectronic
material. To realize this potential, a great deal of work has been done to identify
newapproachestobothnandp-typedoping.Chapter8looksattherapidlyexpand-
ing class of multi-cation TCO materials. Recent work shows that much higher
performance can be achieved in some TCO materials by the addition of elements
thatservetomodifydefectandelectronicbandstructure.Thisabilitytocreatemulti-
componentTCOmaterialswithoutsignificantlydegradingkeytransportparameters
(e.g., carrier mobility) is a characteristic of the TCO class of materials. Chapter 9
looksatthetheoreticalframeworkusedtodescribethebandstructuresofbothn-and
p-type oxide materials and includes a discussion of emerging non-oxide based
transparent conductors. This fundamental backgroundprovides the basis for a dis-
cussion on considerations for the discovery of new high performance transparent
conductingmaterials.Chapter10considersnewmaterialsthathaveemergedinthe
transparentconductorfieldoverthelastfewyears.Historically,thesetofelements
whose oxides provide useful TCO properties have been constrained to single or
mixed oxides of In, Ga, Zn, Sn, and Cd. This chapter discusses how the pallet of
useful elements for TCO applications has grown to open whole new classes
ofmaterials.
ThesecondhalfofthebookbeginstoaddresstheapplicationsofTCOsandhow
new materials can significantly change the paradigm for a technology or be
enabling for another. Chapter 11 discusses the application of TCO materials for
solar energy and energy efficiency applications. In fact, though a key focus is the
active devices like PV, the reality is that in terms of energy efficiency, the use of
TCO’s in energy conservation applications are greater in the near term than
Preface vii
production. In any case it needs to be looked in an integrated way which is the
themeofthechapter.Chapter12considerstheideathatTCOsneednotbeplanar
films but that in many cases the films can be enabling or integrated into a more
complexhybrid(organic/inorganicforexample)devicebyhavingananostructured
morphology. Enabling this is a broad set of solution and PVD approaches to
creating controlled nanostructures in TCO materials from texture to nano-rods
etc. Chapter 13 explores the application of amorphous TCOs and their semicon-
ducting/insulatingTOScounterpartstodevelop newflexibleandtransparentelec-
tronics for displays and more. The demonstration of TOS materials as a channel
materials in thin film transistor applications has dramatically altered the potential
for amorphous oxides in an increasingly diverse set of technologies. Chapter 14
considers the potential for makingtrue oxide based p/njunctions torealizeactive
devices that are entirely based on TCO/TOS materials. The ability to make such
junctions expands the potential for oxide based electronics including transparent
electronics,oxidebasedsolarcellsandLED/lasers.Finally,Chap.15discussesthe
scalingofTCOmaterialstolargeareaindustrialprocessing.Thisisakeyissueasit
addressessomeofthecriticalpropertiesdependenceonprocessparameters.
We note that there is increasing interest in solution processed transparent con-
ductors consisting of nanostructures of carbon (nanotubes), oxides (nanorods i.e.,
ZnO)andmetals(suchasAgnanorods).However,thusfaralthoughtheyarevery
interesting, these materials still have conductivities approximately an order of
magnitude below those for high performance TCOs. Over the next few years we
expectthesematerialswillbecomeincreasinglyimportantperhapsincombination
withTCOmaterials.Theirinclusioninthisvolumeatpresentis,however,beyond
theintendedscopeofthispublication.
Thisbookpresentsapictureofanimportantclassofmaterialsthathas,inrecent
years, drawn increasinginterestforapplicationsinactivedevices andasacritical
component in any structure that requires both electrical connectivity and optical
transparency.Despitetheirtechnologicalimportanceandrelativelylonghistoryof
use,ourunderstandingoftheexistingsetofTCOmaterialsareonlynowreceiving
the kind of combined fundamental/experimental materials research attention that
willinevitablyleadtonewmaterialsdiscoveriesandnovelapplications.Overall,it
isclearthattransparentconductiveoxidesandtransparentconductorsareavibrant
fieldthatisadvancingrapidlyacrossaneverbroadeningspectrumofapplications.
Wehopethisbookwillprovideavaluablereference forthoseinterestedinthe
topic and stimulate additional development of new TCO materials and their
applications.
DavidGinley(Editor)
HideoHosonoandDavidPaine
(AssociateEditors)
.
Contents
1 TransparentConductors ................................................. 1
DavidS.GinleyandJohnD.Perkins
2 ElectronicStructureofTransparentConductingOxides ............ 27
J.RobertsonandB.Falabretti
3 Modeling,Characterization,andPropertiesofTransparent
ConductingOxides ....................................................... 51
TimothyJ.Coutts,DavidL.Young,andTimothyA.Gessert
4 CharacterizationofTCOMaterials ................................... 111
DavidC.Paine,BuragYaglioglu,andJosephBerry
5 InBasedTCOs .......................................................... 149
YuzoShigesato
6 TransparentConductingOxidesBasedonTinOxide ............... 171
RobertKykyneshi,JinZeng,andDavidP.Cann
7 TransparentConductiveZincOxideandItsDerivatives ............ 193
KlausEllmer
8 TernaryandMultinaryMaterials:Crystal/Defect
Structure–PropertyRelationships ..................................... 265
ThomasO.Mason,StevenP.Harvey,andKennethR.Poeppelmeier
9 ChemistryofBandStructureEngineering ........................... 295
ArtSleight
ix
x Contents
10 Non-conventionalMaterials ............................................ 313
HideoHosono
11 ApplicationsofTransparentConductorstoSolarEnergy
andEnergyEfficiency .................................................. 353
ClaesG.Granqvist
12 NanostructuredTCOs(ZnO,TiO ,andBeyond) .................... 425
2
DanaC.OlsonandDavidS.Ginley
13 TransparentAmorphousOxideSemiconductorsforFlexible
Electronics ............................................................... 459
HideoHosono
14 Junctions ................................................................. 489
HiromichiOhta
15 ProcessTechnologyandIndustrialProcesses ........................ 507
MamoruMizuhashi
Index .......................................................................... 527
Contributors
Joseph Berry National Renewable Energy Laboratory, Mail-stop 3211, 1617
ColeBlvd,Golden,CO80401,USA
David P. Cann Associate Professor of Materials Science, Department of
MechanicalEngineering,303DDearbornHall,OregonStateUniversity,Corvallis,
OR97331,USA,[email protected]
Dr. Timoth J. Coutts Research Fellow Emertus, National Renewable Energy
Laboratory,1617ColeBlvd.Golden,CO80401,USA
Dr. Klaus Ellmer Dept. solar fuels, Helmholtz-Zentrum fu¨r Materialien und
Energie Berlin GmbH, Hahn-Meitner-Platz 1, 14109, Berlin, Germany, ellmer@
helmholtz-berlin.de
BarbaraFalabretti DepartmentofEngineering,UniversityofCambridge,Trum-
pingtonStreet,Cambridge,CB21PZ,UK,[email protected]
Dr.TimothA.GessertGroupManager ThinFilmPhotovoltaics,NRELNational
Center For Photovoltaics, 1617 Cole Blvd, Golden, CO 80401, USA, Tim.
[email protected]
David S. Ginley Research Fellow Group Manager Process Technology and
AdvancedConcepts,NRELSERFW102,15313DenverWestPkwy,Golden,CO
80401,USA,[email protected]
Claes G. Granqvist Professor Solid State Physics, Department of Engineering
Sciences, The Angstrom Laboratory Uppsala University, Uppsala, SE-75121,
Sweden,[email protected]
Steven P. Harvey Institute of Physical Chemistry, RWTH Aachen University,
Landoltweg2,AachenD-52056,Germany
xi