This paper updates some of n-tech Research's perspectives on Perovskites, the new wonder material for solar photovoltaics (PV).

1. n-tech Research Article
Perovskite PV: Updating Our Views on Progress
and Commercialization Timelines
Issue date: June 2015
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Perovskite PV: Updating Our Views on Progress and Commercialization Timelines
Perovskites, the new wonder material for solar photovoltaics (PV), continue to garner
impressive attention. Its ascendance has been so impressive that two of the pioneers of
dye-sensitized solar (DSC), Dyesol and Oxford PV, are betting their futures on it. For
good reasons has this material captured everyone's fancy:
• Efficiency levels in labs have soared from ~5 percent to over 20 percent in
barely four years, an unprecedented trajectory in the solar PV field. More
progress is anticipated -- perhaps 25% efficiency or beyond -- as more is
learned about perovskite structures and how to tweak them
• Improved efficiency means using thinner films, which means less material is
used, which brings costs down
• Less energy is lost from activation and regeneration, which means significantly
higher voltages are achievable
• Perovskite works with familiar wet chemistry techniques and simple benchtop
processes, vastly simpler than other solar PV technologies
• That also implies much simpler manufacturing at larger scale, and also points
to more stable lifetimes -- though both have yet to be worked out
The Latest Research: Fast Learning
One estimate suggests there are more than a thousand labs worldwide now working on
perovskite materials. Much has to be not only improved in perovskite-based PV, but the
material itself is wide open for further exploration and understanding. Recent progress in
the past few months illustrates just how high the ceiling -- and hurdles -- seem to be.
 Researchers from the University of Washington and Oxford University took a
closer look at the structural composition of perovskite crystals, finding flaws that
limit electron movement -- and improving them could jack up their efficiency.
 South Korean researchers created an NREL-confirmed 20.1% efficient perovskite-
based solar cell in November 2014, combining methylammonium lead halide
perovskite materials with formamidinium lead iodide and an unspecified "new
fabrication process." Adjusting that materials ratio to about an 85%/15% mix
resulted in cell efficiency to 18.4% and improved the perovskite's stability.

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 The VTT Technical Research Centre of Finland also is working on R2R
manufacturing methods, initially for organic solar cells but also exploring how they
could be used for perovskite solar panels.
Still Some Big Hurdles
Summed up, the promises are immensely attractive: delivering most of OPV's benefits
with efficiencies surpassing thin-film technologies and rivaling c-Si PV, and utilizing much
simpler and cheaper manufacturing processes. At this point, though, the hurdles remain
the same, and familiar to any organic materials-based device: proving it can be produced
in large areas, and with long lifetimes in the neighborhood of other solar PV products.
In both areas, perovskites are still at lab-scale: sizes are in terms of cm2 , and lifetimes
are measured in months instead of years. Some of these issues can be solved by applying
lessons learned already in DSC and OPV, and more broadly by OLED technologies (e.g.
displays and lighting panels), but more improvements and time are still needed.
Acknowledging the issue of encapsulation and device reliability, Dyesol recently
committed to incorporating EFACEC's (Portugal) laser assisted glass frit sealing
technology, touting it as "an essential element" in its market entry strategy. This low-
temperature process has "demonstrated excellent performance in both low temperature
applications and high-speed processing," and has the potential for 20-year-plus lifetimes
for solid-state DSC, according to the company.
Dyesol also says it is working with a device architecture that eliminates not only the back
contact conductors but also the conventional organic hole-transport material.
Oxford PV, meanwhile, says its perovskite cells have achieved IEC mark of 1,000
hours/85°C/85% humidity under IEC testing, and are reportedly "well on the way" to 2,000
hours. Dyesol cites work showing similar demonstration of durability.
Other recent efforts to improve perovskite device size and reliability:
 Japanese researchers turned to vacuum-evaporation to create the top layer of a
perovskite cell, instead of spin-coating it. They claim to have reduced the cell
thickness by a factor of three to 70nm, while eliminating pinholes; lifetime improved
from "a couple of days" to more than a month.
 Research from Brown University (U.S.) promotes a room-temperature solvent bath
instead of high-temperature thermal annealing, potentially suitable for R2R
processing of hybrid perovskite/thin-film solar cells. Their "solvent-solvent
extraction" process was shown to create cells with average conversion efficiency
of over 10% for semitransparent cells (<100nm thickness) and a high mark of

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15.2%. They also claim full coverage without pinholes, and the process takes less
than two minutes.
 Researchers at Los Alamos National Labs have shown a solution-based "hot
casting" technique to grow solar cells from large-area (millimeter-scale) perovskite
crystals, with conversion efficiencies approaching 18%. The cells were said to
demonstrate little cell-to-cell variability and devices showing hysteresis-free PV
response. Reducing bulk defects and improving the charge-carrier mobility in
large-grain perovskite materials were credited for the good performance.
Hybrid Devices: The Future?
Perovskites also are being explored in combination with c-Si and thin-film PV to create
more efficient hybrid devices. There has been some interesting work done recently in this
area:
 In March 2015, researchers from Stanford and MIT reported a tandem perovskite-
silicon device achieving 13.7% efficiency. They used degenerately doped p-type
and n-type silicon to form a tunnel junction, with a TiO2 layer as a contact to allow
electrons to flow through from the perovskite layer down through the tunnel
junction layer to recombine with holes from the silicon layers. Using a serial
connection, their reported open-circuit voltage (Voc) was 1.65V, essentially the sum
of both top and bottom cells. Further improvements are anticipated, from improving
the quality of the perovskite layer to better passivation of the back contact.
 In January 2015, that same Stanford research group published work about creating
tandem solar cells using perovskite with both CIGS and silicon layers. They added
a semi-transparent 12.7% efficient perovskite solar cell in a mechanically stacked
tandem configuration onto CIGS and low-quality multicrystalline silicon layers.
 Oxford PV has been working to add perovskites onto silicon cells, claiming the
combination could ratchet up efficiencies by five percentage points. One simulated
example suggests a 10MW solar farm converted to silicon PV panels with a
perovskite "boost" would become a 12MW plant, generating an additional 3,166
MWh/year and shaving half a year off the payback period.
Commercial Preparations: The Countdown Begins
Dyesol has pledged to have a production prototype device in 2015, a pilot line in 2016 or
2017, and mass production by 2018. The company has agreements with Turkish partner
Nesli for a 50-50 joint venture, with pledged backing from the Development Bank of
Turkey (TKB). A proposed $1.9 million prototype facility in the city of Mersin would

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produce 20,000 m2 volumes annually, followed by a 600-MW fab with "multi-million
square meters annually."
Note that TKB's pledged support is in the form of a letter-of-intent, and project financing
will depend on "its own appraisal of the project" once the business plan is filed later this
year. Also note that Dyesol claims TKB is considering taking a stake in the firm as well,
which it suggests could further provide tax and labor benefits for said operations. At the
same time, Dyesol says it is exploring partnerships in other geographic regions, and
claims to be in "similar negotiations for the financing of at least one other project."
Oxford PV, meanwhile, has consistently maintained it's on track for mass production in
2017. The firm secured £8 million in funding in March 2015, the first tranche of a Series
B round -- more than doubling the company's equity raised to date -- claiming participation
from "a wide range of new investors from the U.K., U.S., Asia, and Europe."
New leadership also is coming on board: former Süss Microtec leader Frank Averdung
stepping in for CEO/co-founder Kevin Arthur, and Simon McClatchie to lead perovskite
product development activities, with experience from a number of process tool companies
(Oxford Instruments, Trikon Technologies, LAM Research, Oerlikon). Such leadership
changes are not uncommon for young companies as they prepare to make the leap to
commercial production. Indeed, Averdung's stated marching orders are to "concentrate
on preparing the technology for scale up" and "securing early commercial agreements."
Another perhaps worth watching in this space is start-up Saule Technologies, founded in
2013 and currently developing a semi-transparent cell on PET film using inkjet processes.
Reportedly their cells are 3% efficient but with plans to get to 10% within two years. The
goal is to spray the precursor material onto adhesive backings, for application on mobile
devices -- for this application, lower efficiencies and low-cost production would trump
multi-year lifetimes.
Our Take: In Search of a Catalyst
What kind of challenge does perovskite pose to other solar PV technologies? Thin-film
PV (particularly CIGS) and perovskites would seem to have some overlaps in targeted
end markets, most especially BIPV. Silicon-based PV, meanwhile, rules the world of flat-
panel PV installations on buildings and ground-mount fields.
Interestingly Dyesol claims it will go after utility, rooftop, and stand-alone installations first,
and then target building integrated applications (BIPV) "in later development stages."
Company assessments suggest materials pricing of as little as $2/m2 , less than a tenth
of current liquid DSC materials.
Tandem cells with perovskite and CIGS/silicon would seem to present the earliest
opportunity to get this technology into end markets of BIPV and eventually flat-panel solar
systems. However, BIPV has stubbornly resisted breaking out into a major end-market.

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c-Si technology and manufacturing is well established, but a glaring lack of profitability
means changes and cost-adders are deeply scrutinized.
We applaud Dyesol and Oxford PV's commercialization plans, although to our thinking a
2017-2018 timeframe still feels a little aggressive. What we will continue to watch for,
however, is how all the research interest in perovskites -- in labs and by hopeful suppliers
-- may eventually evolve into actionable interest from investors. More improvements,
particularly in hybrid devices and low-cost production techniques, likely will attract interest
from within the industry and also from capital markets. As technology sector histories
have shown, that's often the true catalyst to solving development and commercialization
issues and getting products ready for markets.
Author:
Jim Montgomery fulfills the role of Industry Analyst for n-tech Research leveraging his
decade and a half covering various business and technology markets, delivering a wide
range of content to broad B2B/B2C audiences in renewable energy, new electronics, and
semiconductor manufacturing. Before joining n-tech, he was associate editor at
RenewableEnergyWorld.com, reporting on trends in solar and wind technologies,
policies, and finance; examples include early offshore wind energy development in the
U.S., state-by-state analysis of solar energy support, and New York State's potential for
renewable energy integration. At n-tech he has authored or managed reports related to
BIPV, organic photovoltaics and next generation PV materials.
He can be reached at jim@ntechresearch.com
See our related research:
Materials for Next-Generation Photovoltaics