Three Dimensional Solar Cells Based on Optical Confinement Geometries

178 Pages·2013·4.397 MB·English

by  Yuan Li (auth.)

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Yuan Li
Three Dimensional
Solar Cells Based
on Optical Confinement
Geometries
Doctoral Thesis accepted by
Wake Forest University, USA
Author Supervisor
YuanLi DavidCarroll
DepartmentofPhysics DepartmentofPhysics
WakeForestUniversity WakeForestUniversity
Winston-Salem,NC,USA Winston-Salem,NC,USA
ISSN2190-5053 ISSN2190-5061(electronic)
ISBN978-1-4614-5698-8 ISBN978-1-4614-5699-5(eBook)
DOI10.1007/978-1-4614-5699-5
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Supervisor’s Foreword
Three-dimensional(3D)opticalgeometriesarebecomingmoreandmorecommon
intheliteratureandlexiconofsolarcells.Designedtoimprovetheoverallperfor-
mance of a general absorber by employing optical confinement, the concept is
meant to approach the thermodynamic limits allowed by the absorbers chosen.
Currently there are several geometries under study, fromspheresto boxes. Inthis
work, the principles for fiber and tube geometries are worked out in detail.
However, as we show through a combination of optical modeling as well as data
directlyfromsuchdevices,theprinciplesuncoveredarequitegeneralandprovide
an important insight into the challenges of using such geometries with real, com-
merciallyviableabsorbers.
Specifically,thisworkdescribesandrevealsthebasicoperationalnuancesof3D
photovoltaics using three standard tools found in the field: equivalent circuit
models, optical path ray tracing in the cavity, and absorber spectral response.
These tools help us explain our experimentally observed absorption profiles and
correspondingJsc,Voc,fillingfactors,andEQEforsuchdevices.Inthiswork,they
are applied toindividual optical confinementgeometrydevices, integrated optical
confinement geometrydevices, and hybrid optical confinementgeometry devices.
Finally, we discuss the overall picture of these fascinating approaches to high-
efficiencysolarandpointthewaytotheirpotentialinsolarfarms,etc.
April2012 DavidCarroll
v

Acknowledgements
First, I thank my supervisor Prof. David Carroll, who allowed me the freedom to
pursue what interested me. During times when I would hover in a valley of
scientific puzzle, hewas always able toguide me through it.Without his support,
Icouldnothavecompletedandreleasedmyworkofthepastthreeandhalfyears.
IwouldliketoshowmygratitudetoProf.Kim-ShapiroandProf.Williams,who
are my RAC committee. They gave me many great suggestions on my research.
I am indebted to many people within Wake Forest University for making this
projectpossible.
My wife Dan Xue, the most beautiful and kindest girl I have met, not only
prepareddeliciousfoodforme,butalsohelpedmewithcodingandwebdevelop-
ment. My biggest contribution in this work — a web-based photovoltaic analysis
platform(OPVAP,www.opvap.com)—hasmainlycomefromherassistance.
I would also like to thank the following members of Prof. Carroll’s group for
beingexcellentteammates:Wanyi,Wenxiao,Rob,Eric,Bob,Yonghua,andespe-
cially Huihui Huang and Mingjun Wang. If, say, Dr. Carroll guided me towards
thedirectionofbrightness,theyarethepersonswhowentthroughthevalleywith
me.IespeciallyappreciatethecontributionandleadershipofMingjunonthework
oftube-basedDSSC,makingthisthesismorecomprehensiveinthestudyofhybrid
3Dsolarcell.
ThecollaboratorsDeweiZhao,XiangWan,JunmingLi,Pro f.FujunZhang,and
Prof.XiaoweiSunhaveprovidedassistanceandsupportonmanyoccasions.Xiang
WanprovidedstrongsupportinMathematics,whichhasbeenpublishedinPRB.
Anotherfriend,onewhoImustuseaseparateparagraphtoexpressmythanks,is
Dr.XiaoXu.WhenIcametoWakeForestthreeyearsago,hepickedmeupfrom
the airport with another friend, and then, like a “Survival Manual,” he introduced
me to new friends, took me shopping and to a party, even gave suggestions for
researchandcoding.Ihopemorecontributionsandcollaborationswillcomefrom
ourfriendshipinthefuture.
Finally,Ithankmyparents.Theyhavealwayssupportedmychoices,anddotheir
best to assist me in whatever problem Imeet.Also, I want toextend thanks toall
relativesandfriends,pastandcurrent,forallowingmetofinishmyPh.Dsmoothly.
vii

Contents
1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 SolarEnergyandSolarCell. . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 PhysicsofPhotovoltaics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2.1 PhotovoltaicEffect. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2.2 LightDistributioninMultilayers. . . . . . . . . . . . . . . . . . . 7
1.2.3 Drift,DiffusionandRecombination
ofChargeCarrier. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
1.2.4 EquivalentCircuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
1.3 DevelopmentofOpticalConfinementGeometry
SolarCell. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
1.3.1 SeveralApproachestoImproveOptical
PerformanceofOrganicPhotovoltaics. . . . . . . . . . . . . . . 27
1.3.2 ArchitecturesofOpticalConfinement
GeometrySolarCell. . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
1.3.3 TheoreticalModelsandSimulation
of3DSolarCells. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
References. . . . . . . . . .. . . . . . . . . . . . . .. . . . . . . . . . . . .. . . . . . . . 35
2 EquivalentCircuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
2.1 EquivalentCircuitModel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
2.2 HeterogeneousIllumination. . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
2.3 DependenceofLightIlluminationIntensity. . . . . . . . . . . . . . . . . 51
References. . . . . . . . . .. . . . . . . . . . . . . .. . . . . . . . . . . . .. . . . . . . . 55
3 OpticalPathinCavity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
3.1 OpticalPathModel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
3.1.1 IncidenceandTransmission. . . . . . . . . . . . . . . . . . . . . . . 60
3.1.2 AttenuationandAbsorption(Energy). . . . . . . . . . . . . . . . 63
3.2 SimulationMethod. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
3.3 DependenceofIncidentAngleandArchitecture. . . . . . . . . . . . . 67
References. . . . . . . . . .. . . . . . . . . . . . . .. . . . . . . . . . . . .. . . . . . . . 71
ix
x Contents
4 SpectralResponse. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
4.1 TransferMatrixModelforOpticalConfinement
Geometry. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
4.2 ActiveLayerThicknessDependence. . . . . .. . . . . .. . . . . . .. . . 76
4.3 AbsorptionandEQE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
References. . . . . . . . . .. . . . . . . . . . . . . .. . . . . . . . . . . . .. . . . . . . . 79
5 IndividualOpticalConfinementGeometryDevice. . . . . . . . . . . . . . 81
5.1 FiberBasedSolarCellwithDipCoatingITO. . . . . . . . . . . . . . . 81
5.1.1 FabricationofFiber-BasedSolarCell. . . . . . . . . . . . . . . 83
5.1.2 PerformanceofFiber-BasedSolarCell. . . . . . . . . . . . . . 85
5.2 ITO-FreeTubeBasedSolarCell. . . . . . . . . . . . . . . . . . . . . . . . . 93
5.3 TandemOCGPV. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
5.3.1 SerialConnection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
5.3.2 ParallelConnection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
References. . . . . . . . . .. . . . . . . . . . . . . .. . . . . . . . . . . . .. . . . . . . . 101
6 IntegratedOpticalConfinementGeometryDevice. . . . . . . . . . . . . . 105
6.1 FiberBundles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
6.2 AlignedStampedFiberDevices. . . . . . . . . . . . . . . . . . . . . . . . . 105
6.2.1 AlignedStampedFiber(Dome)Devices. . . . . . . . . . . . . 106
6.2.2 AlignedStampedFiberDevices(Long). . . . . . . . . . . . . . 110
6.3 Cones-BasedFiberDevice. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
6.4 ZnONano-rodInvertedSolarCell. . . . . . . . . . . . . . . . . . . . . . . 113
References. . . . . . . . . .. . . . . . . . . . . . . .. . . . . . . . . . . . .. . . . . . . . 120
7 HybridOpticalConfinementGeometryDevice. . . . . . . . . . . . . . . . 123
7.1 Photovoltaic-ThermalSolarEnergyCollectors
BasedonOpticalTubes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
7.1.1 FabricationofTube-BasedPV/TDevices. . . . . . . . . . . . . 125
7.1.2 PerformanceofTube-BasedPV/TDevices. . . . . . . . . . . . 125
7.2 Dye-SensitizedTube-BasedSolarCell. . . . . . . . . . . . . . . . . . . . 129
7.2.1 FabricationofTube-BasedDSSC. . . . . . . . . . . . . . . . . . 130
7.2.2 PerformanceofTube-BasedDSSC. . . . . . . . . . . . . . . . . 132
7.3 Fiber-BasedHybridSolarPowerSystem. . . . . . . . . . . . . . . . . . . 134
References. . . . . . . . . .. . . . . . . . . . . . . .. . . . . . . . . . . . .. . . . . . . . 137
8 Conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
8.1 Summary. . . .. . . . .. . . .. . . .. . . . .. . . .. . . .. . . . .. . . .. . . 141
8.2 SuggestionsfortheFutureInvestigations. . . . . . . . . . . . . . . . . . 141
References. . . . . . . . . .. . . . . . . . . . . . . .. . . . . . . . . . . . .. . . . . . . . 144
9 Appendices. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
9.1 InstrumentsandTools. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
9.1.1 DipCoater. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
9.1.2 RotatingDeposition. . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
9.2 DeviceFabrication. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145