next generation
SILICON solar cell
technology
Cu-plated large-area silicon solar cell with 20,8% efficiency.
ENERGY,
THE CHALLENGE OF THE 21ST CENTURY
Generation of clean energy is one of
the main challenges of the 21st century.
Solar energy is the most abundantly
available renewable energy source which
could be supplying more than 50% of
the global electricity demand in 2100.
Imec uses its expertise in the domains of
nanotechnology, device physics, process
technology and advanced analysis and
modeling to provide industry-relevant
solutions for photovoltaic (PV) energy
generation. As crystalline Si solar cells are
expected to remain the most widely used
PV technology for quite some time, imec
has an important focus on silicon solar
cells. Imec’s silicon solar cells research
concentrates on the development of
high-efficiency cost-effective and industry
relevant solar cells.
As part of the Solliance alliance, imec is
also working on organic photovoltaics
and alternative materials for CIGS solar
cells. These thin film PV technologies can
include new features such as flexibility and
transparency which will fuel a wide range
of new PV applications.
Together with the industry, imec develops
short-term solutions which can be
implemented in production lines in short
term, and does mid- and long-term R&D
involving the development of new device
concepts, characterization and deposition
techniques, laser technologies and various
other processing steps (such as e.g. copper
metallization). Imec is also exploring PV
system innovations broadening its PV
activities beyond pure cell R&D. This
includes e.g. the possibility of integrating
electronics, energy storage, energy yield
optimisation, etc. into the PV system. In
this way the added value of solar energy in
the global renewable energy arena will be
further increased.
Small area interdigitated back contact solar cells (IBC) with 23,3% efficiency.
PERC & PERT:
IBC:
I-module:
Large-area p-type PERC and n-
Interdigitated back contacts
Towards future smart modules
type PERT solar cells
Imec has developed a high-efficiency baseline
process for interdigitated back contact (IBC) solar
cells within its multi-partner silicon solar cells
industrial affiliation program resulting in efficiencies
of over 23,3% on Fz and Cz n-type silicon wafers.
The cells are 2cm x 2cm processed in a 5 by 5 array
on large area 156mm x 156mm wafers. Currently
the focus of research is on process simplification
and module integration. Regarding cell and module
integration a first challenge is to design the IBC cell
such that the performance is not limited by series
resistance while thick metal stacks are avoided.
The second challenge is to develop a cost effective
process flow for module integration.
Although the silicon feedstock price has come
down significantly, the cost of the silicon wafer
is still a considerable part of the solar cell
cost. Hence, reducing the silicon content by
reducing the silicon wafer thickness remains
important for future low cost solar cell
manufacturing. When cells become too thin
to handle and process efficiently, a solution is
to make thin silicon foils and place these foils
onto the module glass plate in an early stage
of manufacturing (the i-module concept).
These foils are then further processed into
solar cells on module level. Next to silicon
wafer cost reduction, this concept also
allows module level processing of e.g. the
cell interconnections and the integration of
additional electronics in the module for e.g.
power conversion and load optimization.
Imec’s proprietary PERC and PERT processes
maximize the conversion efficiency of cells
through structure and material optimizations while
maintaining cost effective device concepts and
processing.Today’s baseline p-type Si PERC process
flow on 156mm x 156mm wafers is industrially
applicable and contains advanced homogeneous
emitter and front-side metallization, rear-side
dielectric passivation with a local Al (aluminum)
back surface field. N-type PERT cells with a rear
side emitter will allow us to push conventional twoside contacted solar cells conversion efficiencies to
its maximum.
Recent developments:
New Ni/Cu/Ag metallization processed
in one plating sequence, resulting in higher
efficiencies and reduced cost. P-type PERC and
n-type PERT solar cells with Cu front contacts, with
efficiencies upto 20,8%, have been realized in imec’s
pre-pilot line.
Solar cell reliability and standard tab adhesion tests
on imec’s plated Cu/Ni/Ag front contacts show no
correlated influence of these materials on the life
time of the cell and module. This validates the
industrial viability of this technology.
Process development of spatial atomic
layer deposition (ALD) Al2O3 for rear side
and emitter passivation. Large area i-PERCtype silicon solar cells with ALD passivation and
industrial screen printed contacts with a cell
efficiency of 20.2% have been achieved.
Integration of ultra-thin (100 μm), largearea (156mm x 156mm) PERC based
solar cells into a class A PERC module,
demonstrating the robustness and industrial
relevance of the technology.
Recent developments:
Optimisation and simplification of cleaning
processes enables a more cost effective IBC
process without conversion efficiency loss.
Exploration of alternative patterning
techniques such as laser patterning or screen
printing instead of lithography show the possibility
of achieving good patterning performance without
significant conversion loss.
Selective epitaxial processing for the
formation of p+-type emitters in IBC cells show
excellent results, enabling a route for future
simplified cost effective IBC cell processing.
Excellent predictive device simulation
knowledge allows rapid exploration of processing
innovations which are then validated by actual cell
processing.
Recent developments:
Improved porous silicon etching
process enabling a good yielding detachment
layer for 40um thin silicon foils.
Excellent carrier life times achieved in
thin epifoils bonded on glass.
Integration of function cells in the
i-module process flow indicating the
potential of the technology.
Why imec?
Imec is an independent research center,
carrying out R&D programs in which
companies, universities and other
research institutes can participate. We
have dedicated cooperation schemes that
are tuned to the needs of the industry.
Imec is bridging the gap between proofof-concept in the lab and industrial
manufacturing. Benefit from imec’s offer
formed by its unique combination of
energy-relevant competences: 30 years
of experience in photovoltaics and microand nanoelectronics, new materials,
characterization and reliability ...
are explored in a R&D cost, risk and
IP sharing environment. In this way this
research complements and enhances our
partners’ existing proprietary technologies.
Researchers from the partners (industrial
residents) can join imec’s research team
allowing hands-on contribution to the
research while capturing the results and
experience.
Silicon
Solar
cells
affiliation program
industrial
Research program focusing on the
development of cost effective and
industrially applicable crystalline silicon
solar cells with an efficiency of well above
20% based on imec’s 30 years track record.
What we offer?
Solliance
program
Imec offers a variety of business solutions
ranging from research collaborations
at various levels of scope and depth to
license agreements and transfer of IP.
Research program in co-operation with
the Solliance partners focusing on the
development of thin-film solar cells: (a)
organic solar cells with increased efficiency
and life time, (b) CIGS and alternative
materials for CIGS (CZTS).
01 Multi-partner R&D programs
Pre-competitive
research
on
the
development of innovative solar cell
devices, new processing technologies,
equipment & material screening and PV
system improvement. In this way new
technologies towards improved cell
effiencies and lower manufacturing cost
Organic
Photovoltaics
02 Bilateral collaborations
Companies can also partner with imec
under a bilateral agreement, developing
specific
advanced
and
disruptive
photovoltaic technology. Such R&D
programs are jointly defined and may be
tailored towards the needs and applications
of the industrial partner.
State-of-the-art
research facilities
A pre-pilot line for silicon solar cells (S-line,
almost 1000m²) running a base line +20%
efficiency PERC cell process tailored to
develop and refine solar cell processes until
they are ready to be further integrated into
production lines. The equipment is similar
to that of a state-of-the-art, industrial
solar cell production environment, and the
batch size is large enough to allow valid
predictions of averages, standard variations
and yield. Techniques used in the prepilot line include isotropic acidic texturing,
plasma texturing, reduced pressure POCl3
diffusion, large area PECVD deposition
of Si nitride, belt furnace rapid thermal
anneal, in-line ALD, in-line Cu-plating,
a flexible laser platform, a wide range
of measurement and characterization
equipment, and many more.
A pre-pilot line for organic solar cells,
(O-line, almost 200m²), an integrated
processing facility for organic solar cells
with all processing steps needed for
the fabrication and characterization of
state-of-the-art bulk hetero-junction and
small molecules single junction and multijunction organic solar cells
Contact us
imec Belgium
E-mail: Philip.Pieters@imec.be
Phone: +32 16 28 12 59
imec India
E-mail: Tony.Vandenzegel@imec-in.in
Phone: +91 80 40 300 442
imec office Japan
E-mail: Mitsugu.Yoneyama@imec.be
Phone: +81 80 5180 1081
imec office US
E-mail: Eric.Dy@imec.be
Phone: +1 415 480 4519
imec Taiwan
E-mail: Peter.Lemmens@imec.be
Phone: +886 3 5781 115 304
imec The Netherlands
E-mail: Ruben.DeFranciscoMartin@imec-nl.nl
Phone: +31 404 02 0444
imec China
E-mail: Gao.Teng@imec.be
Phone: +86 21 5017 2918
www.imec.be
Imec is a registered trademark for the activities of IMEC International (a legal entity set up under Belgian law as a “stichting van openbaar nut”), imec Belgium (IMEC vzw supported by
the Flemish Government), imec the Netherlands (Stichting IMEC Nederland, part of Holst Centre which is supported by the Dutch government), imec Taiwan (IMEC Taiwan Co.) and
imec China (IMEC Microelectronics (Shangai) Co. Ltd.) and imec India (imec India Private Limited).