abdelilah slaoui
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Silicon Thin Film Solar Silicon Thin Film Solar Cells: Potential & Cells: Potential &
Challenges"Challenges"
Abdelilah SLAOUIAbdelilah SLAOUIInstitut d’Electronique du Solide et des Systèmes InESS
CNRS – Univ. StrasbourgStrasbourg, France
Costel-Sorin.Cojocaru@polytechnique.edu
ECOLEPOLYTECHNIQUE
LPICMUMR 7647Pere Roca i Caboroccas
… more than 300 publications
Since 1975 …
InESS (PHASE) active in PVInESS (PHASE) active in PV
PVInESS
1) High efficiency cells on mc-Si & ribbons (< 100µm)
2) TF-Si cells on foreign substrates
4) Polymer based organic cells (+LIPHT)
3) Advanced concepts(QDs,
plasmonics, RE-TCOs)
contactemetteur
basecontact
substrat
Bulk Si : Eg=1.1 eV
QD cell 1 : Eg=1.5 eV
QD cell 2 : Eg=2 eV
Photovoltaic research at Photovoltaic research at InESSInESS
OutlineOutline
Thin Film Solar Cells Market
Silicon thin film technologies: Polymorphous Si/µc-Si
Polycrystalline Si * Direct deposition approach* Seed layer approach
Si nanostructures (Si-NWs, Si-nps)
Future of TF-Si based technologies
Photovoltaic Techn.in 2009: Market sharesPhotovoltaic Techn.in 2009: Market shares
Source: Paula Mints, Navigant Consulting
• Progress in PV modules production• Si wafer based PV modules still dominant: 84% in 2009• Schipments of TFs ~14% in 2008 & 16% in 2009
Learning Curve for PV modulesLearning Curve for PV modulesHistorical and Projected Experience Curve for PV Modules
Source: GreenTech/Prometheus
a-Si, a-Si, µc-Si, µc-Si, TF c-Si TF c-Siamorphous, microcrystalline, amorphous, microcrystalline, CrystallineCrystalline
TF Silicon basedTF Silicon based ModulesModules
polymorphous polycrystalline
e-
4
Pumping
RF electrode
Plasma
Substrate
SiH4
PH3
GeH4
H2
TMB
Hydrogenated amorphous Silicon (a-Si:H) at Ts < 250°C
Layers deposited from SiHx radicals
- Most widely-used deposition method – PECVD- Strong degradation of efficiency unstable Si-H bonding
Low Ts ~ 200 °CScale up demonstrated
From Amorphous to Polymorphous SiFrom Amorphous to Polymorphous Si
Costel-Sorin.Cojocaru@polytechnique.edu
ECOLEPOLYTECHNIQUE
LPICMUMR 7647
Plasma-formed nanocrystals/clusters contribute to deposition polymorphous silicon(pm-Si:H)
4 nm
Nanostructured material Silicon nanocrystals
in an amorphous matrix
Medium Range OrderImproved transport properties
and stability
From Amorphous to Polymorphous SiFrom Amorphous to Polymorphous Si
100 cm2
mini-module
Costel-Sorin.Cojocaru@polytechnique.edu
ECOLEPOLYTECHNIQUE
LPICMUMR 7647
400 500 600 700 800 900 10000,0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1,0
Rép
onse
Spe
ctra
le
Longueur d'onde (nm)
LitD4_C
µc-Si:H PIN solar cells
Jsc = 24.5 mA/cm2
FF Voc Jsc (%)67.3 0.520 V 24.5 mA/cm2 8.6%
Towards Micromorph Si solar cellsTowards Micromorph Si solar cells
Costel-Sorin.Cojocaru@polytechnique.edu
ECOLEPOLYTECHNIQUE
LPICMUMR 7647
pm-Si:H
Potential micromorph =15%
µc-Si
-Growth from nanocrystals leading to unusually large crystalline domains- Manifests as epitaxy or very-large grain fraction
Si
Si
Towards high efficiency solar cells through Low Pressure Plasma Processes
E.V. Johnson et.al. Appl. Phys. Lett. 92 (2008) 103108
From polymorphous to Crystalline-SiFrom polymorphous to Crystalline-Si
Costel-Sorin.Cojocaru@polytechnique.edu
ECOLEPOLYTECHNIQUE
LPICMUMR 7647
~1 µm thick c-Si film at
LT
c-Si transferred onto a PI film (or on a metal foil)
Costel-Sorin.Cojocaru@polytechnique.edu
ECOLEPOLYTECHNIQUE
LPICMUMR 7647
OutlineOutline
Thin Film Solar Cells Market
Silicon thin film technologies: Polymorphous Si
Polycrystalline Si * Direct deposition approach* Seed layer approach
Si nanostructures (Si-NWs, Si-QDs)
Future of TF-Si based technologies
TF-TF- Crystalline Crystalline SSii solar cells solar cells ??Potential: 2-3 µm Si to reach reasonable efficiency Similar technology than bulk Si No hazardous nor rare elements
ChallengesFast deposition/formation High quality material (Leff >> W)
Good surface passivationEfficient light confinment
F. Llopis, I. Tobıas, SOLMAT 87, (2005), pp.481-492.
• HT-CVD at T>900°C• HT substrates : Alumina, SiSiC, SiN, mullite• High Dep. Rate ~1-5µm/min
5s 120s
10µm
15s
30 sec 60 sec 180 sec
Polycrystalline Si by Direct CVDPolycrystalline Si by Direct CVD
1
3
2
4
pppp++-Si//-Si//FoxFox/ADS09/ADS09
A. Slaoui, et al., SOLMAT, 71/2, 245 (2001)
• small grains large density of GBs many defects• large distribution depletion of grains• Preferentiel grains orientation (110)
Enlarging grains CVD-OVL, seed layer approachNeutralizing defects TREBLE, hydrogenation
CVD @1200°C
Polycrystalline Si by Diect CVD Polycrystalline Si by Diect CVD
A.Focsa, A. Slaoui et al., Renewable Energy 33 (2008) 267–272
Bare mullite
Mullite + PSG
Mullite + BSG
CVD-OLL CVD-OLL Si deposition on Si deposition on Flowable oxidesFlowable oxides (DC) (DC) increased adatom mobility reduce nucleation density
EU-LATECS project: IMEC, Dow-Corning, FhgISE, InESS
Polycrystalline Si by CVD-OLLPolycrystalline Si by CVD-OLL
substrate
Si Seed layer
Si Absorbing layerAluminium induced Crys. Zone (lamps) melting induced RxLaser induced Crys.
VPE / SPE
contact
emetteur
basecontact
substrat
Si < 2µm
BS Glass, Ceramics Glass, HT GlassAlumina, Mullite, SiSiC, Metal foils
Polycrystalline Si: Seed Layer ApproachPolycrystalline Si: Seed Layer Approach
before anneal anneal 5min / 500°C
anneal 10min / 500°C anneal 60min / 500°C
Source: Nast et al.
Polycrystalline Si by AICPolycrystalline Si by AIC
E. Pihan , A. Slaoui, Thin Solid Films 511 – 512 (2006) 15 – 20
Aluminum Induced Crystalization of a-SiAluminum Induced Crystalization of a-Si
Glass
50 µm
Fox/Silicon
Fox/Mullite
Fox/Alumina
th-SiO2
Poly-Si by AIC vs substrate
E. Pihan et A. Slaoui., J. Crystal Growth 305, 2007, pp. 88-98
0
20
40
60
80
100
0 50 100 150 200 250 300 350cr
ysta
llize
d fr
actio
n (%
)
annealing time (min)
500°C 475°C
450°C
AIC poly-Si layer on glass-ceramic substrate
Growth Kinetics
EBSD analysis: grains size &
grains orientation
Defect analysis using EBSD Technique
475°C/3h
black lines→high anglered lines → Σ3 twingreen lines → Σ9 twin
Polycrystalline Si by AIC on Glass CeramicsPolycrystalline Si by AIC on Glass Ceramics
ANR project - Polysiverre: InESS, Corning, TOTAL, AET, LPICM, INL, EMSE
P. Pathi/A. Slaoui., Applied Physics A, 97 (2009) 45.A. Pathi/A. Slaoui, 24th European PVSEC 2009, 2533.
• Metal (FeNi) as a back contact• development of a conducting barrier layer against metallic imp.
ANR project - CRISILAL: CEA, InESS, ArcelorMital, AnealSys
CSL boundaries
Polycrystalline Si by AIC on Metal FoilsPolycrystalline Si by AIC on Metal Foils
Homojunction - Mesa
Emitter n+
Lcol
Ln
• large charge collection high Isc• large SCR low Voc
ITO
substrate AIC layer (p+ / n+)
Absorber layer (p / n)
Base contactsEmitter contacts
a-Si
Heterojunction - IDC
• Higher Voc• Lower series resistance
AIC + epi-CVD (2.1µm)Voc ~ 450-530 mV
Efficiency ~ 8 – 10%Limited by intragrains defects
O. Tuzun , A. Slaoui et al. , 23 EUPVSECSOLMAT 2010, in press
substrate
AIC layer (p+)
BSF layer (p+)
Absorber layer (p)
Base contactEmitter contacts
Emitter (n+)SiNx
Polycrystalline Si solar cells by AICPolycrystalline Si solar cells by AIC
110nm Si layer experiments
Seed layer by LICEpi-layer
Glass substrate
EU project -HIGH-Ef: IPJ, Horiba, CSG, Bookam, EMPA, InESSANR project -SiLaSol: InESS, ArcelorMital, CEA, Excico, IREPA-laser
anneal
Polycrystalline Si by LICPolycrystalline Si by LICLaser Induced Crystalization of a-SiLaser Induced Crystalization of a-Si
445nm Si layer
Sample
Ar, O2
Ellipsoidal reflector
Linear halogen lamp
CCD-camera
Array of halogen lamps
Si by CVD + Zone Melting recrystallization
Elongated grainsSize: 1-20 mm 11,5% with 10 µm
Si 15,4% with 20 µm Si
0,0 0,1 0,2 0,3 0,4 0,5 0,60
10
20
30pc-Si on mullite substrate
after ZMR
Curre
nt d
ensit
y [m
A/cm
²]
Voltage (V)
S. Bourdais, S. Reber, A. Slaoui, 16th EU-PVSEC, (Glasgow, Ecosse, 2000) p. 1492
no ZMR
Polycrystalline Si by ZMRPolycrystalline Si by ZMR
EU project -COMPOSIT: ISE, IMEC, InESS, RWEEU project-POLYSIMODE: IMEC, InESS, CSG, Helmoltz, ISE
SnO2Glass or flexible sub
Step 4: complete i-n layers on topp-type SiNW
p-t
ype
i-layer n-layer
Strong light trappingRadial junction
Silicon based nanostructures solar cells Silicon based nanostructures solar cells
Vertical SiNWs Si nanostructure tandem cell
Eg=1,5eV
Eg=1,1eVEg3
Eg2
Eg1
Eg1> Eg2> Eg3
Si-nps
Si-nps
c-Si
Eg=2eV
A. Slaoui, R.T. Collins, MRS Bulletin V32 (2007) N°3
Nanostructured Silicon:* SiNWs: light trapping
* Si-nps: photon energy shifter (DC ?)
* Si-nps: New wide BG absorbing Si (tandem)
One pump down “all-in-situ” fabrication of SiNWs on TCO substratesNano-scaled In or Sn drops produced on ITO or SnO2 by H2 plasma superficial reduction at 200oC~350oC.
SnO2 or ITO
H+ H+
Cg
Cg
SiHx (or SiHx +H+)
Cg
SiHx (or SiHx +H+)SiHx
Deposition interface
Diffusion of Si in catalyst drops
Dissolve & absorption
(a)
Sn or In drops
Cg (b)
(c)
(a) (c)
(b)
<110
> (d)
a-Si
2~2.5nm sheathof a-Si
2~2.5nm amorphous layer
(d)
(a) (c)
(b)
<110
> (d)
a-Si
2~2.5nm sheathof a-Si
2~2.5nm amorphous layer
(d)
P.-J. Alet, P. Roca i- Cabaroccas et. al. Journal of Materials Chemistry 18 (2008) 5187
Vertical Si–NWs based solar cells Vertical Si–NWs based solar cells
Costel-Sorin.Cojocaru@polytechnique.edu
ECOLEPOLYTECHNIQUE
LPICMUMR 7647
Challenges- Control catalyst size- Density, position- Transport, doping,…
World record efficiency for a bottom up Silicon Wire Radial Junction Solar cell
Vertical Si–NWs based solar cells Vertical Si–NWs based solar cells
Costel-Sorin.Cojocaru@polytechnique.edu
ECOLEPOLYTECHNIQUE
LPICMUMR 7647
Silicon nanostructure wide Eg material Silicon nanostructure wide Eg material • Engineer a wider band gap material using Si nanostructures• Si QDs-relaxed size constraint cf QW, for given a quantum confinement
Ener
gy P
L (
eV)
Si Nanoparticules size (nm)
MW-PECVD : NH3 + SiH4 Si rich SiNx:H (Si-RSN)
* Single layer
* Multilayers
Si nanostructure tandem cells Si nanostructure tandem cells
anneal
anneal
20 nm20 nm
Delachat, Carrada, Slaoui; Nanotechnology 20 (2009) 415608_1-5Keita, Delachat, Slaoui, J. Appl. Phys. 107 (2010) 093516
BG 29% 33% 37% 44% 50%1 nm - - - ? ?3 nm - - - 1,85 2,05
4 nm - 2,05 x x x5 nm ? x x x 1,37
Si-nps
Si-nps
c-Si
Si nanostructure tandem cells Si nanostructure tandem cells Bandgap value depends on SiNx thickness and on Si excess in SiNx
• Potential : Efficiency ~35%• Chalenges: * Tunneling distance between layers & QDs * Doping * Extraction of carriers
* Cost
The Future of TF-Si based PV Technologies The Future of TF-Si based PV Technologies • Better Control and rational use of materials - Better plasma control - Gas recycling - Faster high-quality TCO’s - Higher deposition/crystallization rates
• New materials - Si-nanowires / Si-nanops - p-type TCO’s - Printable TCO’s - Nanocrystalline diamond, SiC
• Better light management - Improved TCO’s ( Lower IR absorption = lower N; Textured) - Random texture (texture glass; back reflector) - Periodic Structures (Grating, photonic crystals, plasmonics) - Conversion spectrum
Long Term Objectives:-Concepts for stable cells with >17%
Costs<0.4 Euros/Wp at 500 MW, = 15% (rigid)< 0.3 Euros/Wp at 500MW, = 13% (flexible)
Acknowledgements
From InESS/Strasbourg: C. Chatterjee; A. Chowdhury; F. Delachat; A. Focsa; P. Prathap; S. Roques, O. Tuzun; …
ANR–HABISOL projects: CRISILAL, POLYSIVERRE, SILASOLEU Projects: LATECS, CRYSTALCLEAR; HIGH EF, POLYSIMODE
From LPICM/Ecole Polytechnique/Palaiseau:P. Roca i-Cabarocas
Bilateral Conference on Energy
9 – 13 May 2011; Nice / France
http://www.emrs-strasbourg.com/
Bilateral Conference on EnergySymposia:
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