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www.ecn.nl
18.5% efficient n-type silicon solar cellsmade in pilot production.
Towards higher efficiency and lower cost PV
www.ecn.nl
Over 19% efficient n-type silicon solar cellsmade in pilot production.
Towards higher efficiency and lower cost PV
3 7-11-2010
A good example of collaborative effort …..
Newtechnology
Research Institute
PV manufacturer Equipment Supplier
4 7-11-2010
… towards bi-facial n-type solar cells !!!
• n-type: higher quality: higher efficiency• bi-facial: open rear: higher energy production
5 7-11-2010
The old days
ResearchInstitute
PVmanufacturer
EquipmentSupplier
New
Technology
6 7-11-2010
The now days
ResearchInstitute
PVmanufacturer
EquipmentSupplier
New
Technology
Scattering of technology
7 7-11-2010
The new days
Newtechnology
Research Institute
PV manufacturer Equipment Supplier
8 7-11-2010
Demand for innovation
• Most cell producers still use conventional p-type H-bar technology
• Strong need for high efficiency:- Leverages area-related wafer, module and system costs such
as materials and labour- Higher kWh/Wp
• Industrial scale
• ECN n-type cell technology meets requirements
… and speed is needed
9 7-11-2010
PANDA project: towards fabrication
• Yingli- Creating and operating pilot line- Debugging and optimizing pilot operation- Improving the technology- Cost assessment
• Tempress (subsidiary of Amtech Systems)- Diffusion and glass removal equipment- Optimization of diffusion processes
• ECN :- Cell technology- Process optimization
10 7-11-2010
Work horse of PV industry: Al-BSF cell
11 7-11-2010
What held n-type solar cells back?
• Historical: e.g., p-type base better radiation resistant in space
• High-temperature necessary for B-diffusion;but this is problematic only for p-type substrates
• Creating oppositely doped layers on front and back.
• B-emitter passivation.
ECN made breakthroughs in 2005
12 7-11-2010
• Major metal impurities affect n-type less• p-type dopant: boron-oxygen recombination centre.
n-type wafer offers better diffusion lengths
n-type Si
n++ BSF
p++ emitter
Feo/+
Tio/+
p-type Si
(n+) Phosphorous emitter
Fe+/o
Ti+/o
Back contact
B-O2i
Efficiency: record cells
13 7-11-2010
Cell IscA
UocV
FF%
Areacm2
JscmA/cm2
Eff.%
3-44 8.78 638 79.5% 240 36.6 18.58%*
3-12 8.90 635 78.2% 240 37.5 18.65%*
1-16 8.96 638 77.0% 237 37.8 18.59%*
#1 9.00 637 79.6% 237 38.0 > 19.0%
#17 8.98 637 79.5% 237 38.0 > 19.0%
*FhG-ISE, May 2010
Features of the Panda cell• Bifacial cell, on 6 inch CZ wafer.• n-type material for good efficiency
• Phosphorous BSF- good FF
- rear surface passivation.
- allows bi-facial design.• No aluminum BSF: no bending of cells, suitable for thin wafers
• Industrial processing• Metallization:
- industry compatible screen printing
- open front and rear: limited coverage and paste consumption- compatible with standard module manufacturing technology
14 7-11-2010
Pilot line for Panda cells
• Dedicated pilot line available at Yingli- Allowed very rapid development.- Experiment turn-around 1-2 days
• Objectives:- Demonstrate Panda technology- feasibility of production- Improve efficiency- Module manufacture and certification- Bottlenecks.- Specification of fab equipment
15 7-11-2010
Technology improvements in pilot line
• towards up-scalability.
- processing times- number of steps- use of consumables
• Large technological advances, e.g.
- metallization- rear surface passivation
16 7-11-2010
0.4 0.6 0.8 1.0 1.20.0
0.2
0.4
0.6
0.8
1.0
Boron emitter passivation:noneSiNx
NAOS+SiNx
IQE
wavelength [µµµµm]
17 7-11-2010
Breakthrough in passivation
New technique for n-type emitter passivation:15% relative gain in efficiency
Mihailetchi et al.,Appl. Phys. Lett. 2008.
Improved metallization
18 7-11-2010
Uoc Isc FF eta
- +0.14 A +0.6% +0.4%
• Paste slumping and shading• Contact resistance• Line resistance
Original Improved
Improved rear surface passivation
19 7-11-2010
Uoc Isc FF eta
+3 mV +.04A 0% +0.2%
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2
IQE
wavelength
front illum.
rear illum.
improved
reference
From lab to fab …2009-06:
start of Panda project2009-09:
Pilot line up and running
2010-03:Yingli announces 300MW Panda expansion.
2010-06:
Yingli shows first Panda modules2010-07:
Yingli announces initial production of Panda cells and 19% efficiencyreached in pilot line.
2010-10:Yingli announces additional 600MW Panda expansion.
20 7-11-2010
… in just over a year !
What does Panda mean for PV?
21 7-11-2010
• High-efficiency industrial silicon PV technology.
• New silicon cell technology in production
• A new mainstream technology in PV may have emerged
Towards 20% … , and beyond
• Young technology:- Further improvements are possible
• Combine n-type with benefits of MWT / BC technology
22 7-11-2010
23 7-11-2010
Conclusions• ECN’s n-type concept: high efficiency with an industrial process.
• 18.65% confirmed, but > 19% has been achieved
• Involvement of Yingli has hugely accelerated development.
- “From lab to fab” in a little over a year !
Thank you for your attention
24 7-11-2010
25 7-11-2010
n-type solar cell versus p-type solar cell
• Better EQE in infrared: Higher Isc
• Less recombination: Higher Voc and Fill Factor
• Results in at least 5 – 8% efficiency gain over p-type
0
0.2
0.4
0.6
0.8
1
300 500 700 900 1100
wavelength of light (nm)
exte
rnal
qu
antu
mef
fici
ency
(EQ
E)
N-type
p-type 0
200
400
600
800
1000
1200
1400
1600
1800
0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2Wavelength (um)
Irradiance
Photon flux
bandgap Si1.1eV