
World record solar cell with 44.7% efficiency - X4
http://phys.org/news/2013-09-world-solar-cell-efficiency.html
======
TheLegace
"These solar cells are used in concentrator photovoltaics (CPV), a technology
which achieves more than twice the efficiency of conventional PV power plants
in sun-rich locations. The terrestrial use of so-called III-V multi-junction
solar cells, which originally came from space technology, has prevailed to
realize highest efficiencies for the conversion of sunlight to electricity. In
this multi-junction solar cell, several cells made out of different III-V
semiconductor materials are stacked on top of each other. The single subcells
absorb different wavelength ranges of the solar spectrum."

If that isn't a reason to be investing in Space, I don't know what is.

"This world record increasing our efficiency level by more than 1 point in
less than 4 months..."

I think we may start to see Moore's Law starting to be applied to Solar Cells.
Which actually reminds of a chart on the waves of innovation[1] on the
Stanford Tech Entrepreneurship course where we are now seeing the tail of IT
and computing and beginning of renewable technologies. The same thing can be
said about energy density of batteries(According to Tesla batteries).

[1] Page 5
[https://d2d6mu5qcvgbk5.cloudfront.net/documents/original/69b...](https://d2d6mu5qcvgbk5.cloudfront.net/documents/original/69bd3725d86ab970f2d9509424bb67ae4c832faa.pdf?1377910658)

~~~
dpatru
> If that isn't a reason to be investing in Space, I don't know what is.

To justify government research, the results need to be compared to the
alternative. Had NASA scientists not been working for the government, they
would have been working for private companies engaged doing useful work. The
Soviet Union had similar resources to the US, yet their research budget was
spent wholly by government, whereas a large portion of the US research during
that time was directed by private companies. If you want to restrict the
comparison just to the US, ask yourself what would the massive wealth that was
dedicated to NASA had produced had it been directed by private interests? What
would NASA engineers have produced had they been employed by in Y-Combinator-
style startups? (or even big private companies like Google, Apple, Facebook,
Amazon, etc.)

~~~
scarmig
A couple points:

1) It's not like the Soviet Union was a terrible hellhole for research. It had
impressive research output for decades.

2) That's almost beside the point, however. Let's take it as a given that more
good research, whatever that is, is a worthy goal for a society, and that the
market under-invests in it in favor of short term profits. It's obviously not
a binary of either 100% government funding or 100% private; it's not even
really a one-dimensional continuum, because for the large capital expenditures
typically involved in research, the government always has a heavy involvement,
either in tax breaks or grants or collaboration. The question is, how do we
allocate money to produce the best research? It's undoubtedly at some value
that's somewhere between 0% and 100%.

3) There's a whole lot of money floating around now that makes endeavors like
SpaceX practicable. That wasn't the case in, say, the Sixties. Even if the
arguments for government spending on research were weak now, they'd be
stronger in the 1960's, particularly for things like space exploration that
required substantial concentrations of capital.

~~~
snippyhollow
As great as SpaceX is, at least half of its funding comes from NASA
[https://en.wikipedia.org/wiki/SpaceX#Funding](https://en.wikipedia.org/wiki/SpaceX#Funding)

~~~
JanezStupar
I believe that SpaceX would have no problem securing funds from either BRIC,
Arabs or even AlQuaeda for that matter.

------
dredmorbius
For those wondering about the significance of this announcement:

As several people have noted, what matters for solar PV isn't _efficiency_ but
_cost per Watt_. The maximum _available_ energy is 1W/meter^2 at ground.
Single-layer PV efficiency is on the order of about 40%. Mutliple-layer cells
can reach a maximum of around 80%.

Even with existing efficiencies, the land space necessary to dedicate to solar
power for all electrical energy needs is reasonably small. A percent or so of
the Earth's surface. The hard part will be fabricating the PV and/or CSP
(concentrated solar thermal power) plants to collect that energy, estimates
run well over $100 trillion globally (Jacobson & Delucchi).

A key limiting factor in solar, wind, and other intermittent renewables is
_storage_ (or baseload / standby power). Assuming you'd want 7 days' total
energy output on reserve, there's quite literally not enough lead in the world
to build storage for just the US, let alone the rest of the world. Pumped
hydro storage is very efficient, but sites are limited. Biomass similarly
doesn't scale to present populations. Geothermal is good for 5-20% of power
demands depending on locations (and some places such as Iceland might be able
to export energy). Thorium reactors look like a plausible bet but require
development. Liquid metal / molten salt batteries (such as Donald Sadoway's
designs) look like they're both cheap and abundant enough to make the grade,
though they're still under development as well.

Solar power _does_ have its equivalent of Moore's Law: Swanson's Law. Solar PV
costs fall by 20% with each doubling of capacity. It's held since the 1970s
and looks likely to continue. Effectively, costs half about every 3 years.
[http://www.economist.com/blogs/graphicdetail/2012/12/daily-c...](http://www.economist.com/blogs/graphicdetail/2012/12/daily-
chart-19/print)

In short: this is mostly of significance for applications in which space
and/or weight are at a premium: satellite or possibly solar-powered aircraft
(ultralights or airships most likely). For ground-based generation, look for
costs to come down further.

And pray for highly effective storage solutions.

~~~
forgottenpaswrd
"The maximum available energy is 1W/meter^2 at ground"

Where are you from, Britain?

[http://en.wikipedia.org/wiki/Sunlight](http://en.wikipedia.org/wiki/Sunlight)

""sunshine duration" to mean the cumulative time during which an area receives
direct irradiance from the Sun of at least 120 watts per meter"

"The total amount of energy received at ground level from the sun at the
zenith is 1004 watts per square meter"

This depends on altitude of course, the maximum is over 1300W in space.

~~~
Roboprog
I assumed he meant "1 kW" and missed the k.

~~~
dredmorbius
Quite.

------
twelvechairs
this is great but its worth noting that efficiency isn't really what's holding
solar production back, its price. few peoples roofs are crammed with PV to the
point where they can't fit more in.

~~~
paul_f
This is the fundamental problem with PV. Compared to cheap natural gas, there
just isn't much future in it

~~~
jussij
No Future?

That might be true, except for that rather large elephant in the room call
_human-induced climate_ change.

~~~
diydsp
yes and PP presupposes "cheap natural gas." as witnessed by recent fracking-
induced earthquakes [1] there may be very little cheap natural gas in the
future.

[1][http://www.sciencemag.org/content/341/6142/1225942](http://www.sciencemag.org/content/341/6142/1225942)

------
greglindahl
Odd that the figure says that the efficiency was 44.7% +/\- 3.1% -- given the
big error bar, how could they say they'd increased 1% in 4 months? Measure it
again, who knows what you'll get!

~~~
nazgulnarsil
ERROR BARS DO NOT WORK THAT WAY

~~~
kyberias
Care to elaborate?

~~~
scythe
The +/\- 3.1% is relative to the efficiency. The way to read it is: 0.447 +/\-
3.1%, where now it's more obvious that it translates to more like 0.447 +/\-
0.014.

~~~
greglindahl
Even if it really means 0.447 +/\- 0.014, an increase of 0.01 is not very
significant!

------
sejje
Maybe I missed it in the article, but what was considered a good efficiency
prior to this?

~~~
diydsp
someone on wikipedia has been maintaining a beautiful image of the history of
solar cell efficiency for various technologies.. let's see if this has been
added yet. It looks 1. No, and 2. There was a recent discovery by Sharp of
44.4%.

Main page:
[http://en.wikipedia.org/wiki/Solar_cell_efficiency](http://en.wikipedia.org/wiki/Solar_cell_efficiency)

[http://en.wikipedia.org/wiki/File:PVeff%28rev130923%29a.jpg](http://en.wikipedia.org/wiki/File:PVeff%28rev130923%29a.jpg)

~~~
contingencies
Image is credited to _L.L. Kazmerski_ of the _National Renewable Energy
Laboratory_ (NREL), Golden, CO.

Have a look at the types of markers shown on the image key again. While vast
amounts of resources are being dumped on efficient electricity extraction
through expensive, advanced manufacturing processes, some are looking at going
back to organics, which NREL classes as 'emerging'. Apparently hybrid
organic/electrical photovoltaics date back to 1958, and can produce 11.1%
(roughly 1/3-1/2 of currently available manufactured products) efficiency
while remaining cheap to produce at high volumes. Mitsubishi is one of the
research leaders.

More at
[https://en.wikipedia.org/wiki/Organic_solar_cell](https://en.wikipedia.org/wiki/Organic_solar_cell)

------
ck2
While nearly 45% is impressive, I'd rather see "cheap as paint" solar cells at
10% efficiency that are football fields in size.

Put them on every commercial rooftop and all that free space we have out west
in the USA.

~~~
dmckeon
It is an interesting challenge for a PV-curious homeowner - if efficiency is
increasing, and capital costs are dropping, and assuming that rooftop cells
might eventually need replacing - it is better to cover one's roof all at once
with current tech, or to start smaller and plan to add new panels over time
until the roof is full, and then start replacing old panels?

Local variables would probably predominate, along with loan/lease/financing
and ability to resell.

------
dgreensp
So when does solar power become cheap and efficient enough that it's a real
game changer? It seems like the numbers have gotten a lot better in recent
years, at least in terms of efficiency.

~~~
tsotha
Solar is already cheaper in most places provided you have net metering, which
is a subsidy. But there's a limit to how many people can use the grid for
free.

~~~
evolve2k
Don't forget to take into account that grid connected solar houses feed excess
power produced into the grid, there's no free about it, these are essentially
micro power stations which enhance the grid.

~~~
tsotha
You're missing the point. The free part is they're selling back power at
retail rates. In net metering if you generate as much power as you use you
don't pay any per kWh charges. Where I live the power company is selling power
to consumers for about 22 cents per kWh. From normal wholesale vendors it's
buying power for somewhere around seven cents, but it's buying buying power
from net metering people for 22 cents.

That's where the "using the grid for free" part comes in. People who purchase
wholesale-generated power are paying the power company's overhead, whereas the
net metering people aren't.

~~~
reitzensteinm
In addition, the home owners are selling a electricity at a fixed time and
buying it back with flexibility, not taking into account the spot price of the
electricity (which is going to lower drastically during peak solar times over
the next few decades).

If every home owner installed sufficient solar power to be neutral under net
metering, the grid would have to be maintained, with traditional generation
supplied at off peak solar times _at no cost to the home owner_.

If that doesn't show how heavy a subsidy net metering is, I don't know what
will. It's not sustainable and should never be used to price out solar.

------
SamuelKillin
Good on them. In reality, however, fuel from the sun is free and we have
unlimited land. Getting the cost down and economies of scale are what everyone
is really focussed on.

~~~
tsotha
Who has unlimited land?

~~~
SamuelKillin
I'm in Australia. We have unlimited land and enough sun to power the solar
system.

~~~
tsotha
You guys might be one of the few countries with effectively unlimited land.
But remember the power has to get from where it's generated to where it's
needed.

------
tomasien
I'm going to turn to Hacker News, as I always do, for context: what would 50%
efficiency mean?

~~~
ChuckMcM
Short answer is that more of the solar insolation that hits Earth gets
converted into electricity. So on the equator its about 1kW per square meter,
in North America closer to 700W sq Meter, and converted at 50% you would start
at 350W per sq meter, which after rectification might be 300W per square
meter.

------
rocco
Guys, anyone knows the sense of "measured at a concentration of 297 suns."? is
sufficient much less energy to transform the earth in a giant BBQ.

~~~
asab
My question too - I wonder how it would perform in normal sunlight.

~~~
mchannon
Concentrator cells make a number of tradeoffs in order to make their
performance as high as possible (and keep from melting, etc.). I would guess
around 22% efficient in one-sun AM1.0; that's about what other concentrator
cells in this upper tier do.

If it's slightly cloudy, I could see efficiencies dropping to the single
digits, as each of these cells is actually four different cells all wired in
series, each sensitive to different wavelengths of light. If the blue drops
out, the corresponding cell on the top of the stack acts as a resistor (and it
can even burn out, being so thin).

Solar cell efficiency records (particularly for concentrator applications) are
like discovering new transuranic elements- extremely useful and interesting at
first, then significantly diminishing returns.

------
officialjunk
Now combine this with IBM's research to collect most of the energy lost to
heat production and push the efficiency up to 80%
[http://arstechnica.com/science/2013/04/ibms-solar-tech-
is-80...](http://arstechnica.com/science/2013/04/ibms-solar-tech-
is-80-efficient-thanks-to-supercomputer-know-how/)

------
brownBananas
Is the composition of this one solar cell from 4 subcells of any significance?
Is it just 4 for a reason?

~~~
mchannon
Imagine you have commissioned 100 different manufacturers to make you 100
different arbitrary Lego knockoffs; each manufacturer picks a color,
thickness, and a peg pitch (spacing between the pegs). Each manufacturer only
makes exactly one kind. Some manufacturers' legos will fit together, and some
won't.

Some manufacturers make theirs very cheaply and in mass quantities, and some
will take years to deliver a very small number at very high prices.

As a solar cell designer, you want to make a stack of these legos to form a
rainbow. It has to go from blue on the top to red on the bottom, and it has to
stack together without too much force.

Think of a brand-X terrestrial Home Depot crystalline solar cell as just
yellow lego bricks. They aren't the whole rainbow (and green would actually be
a closer match to sunlight if you could only pick one color) but they're
cheap.

Gallium Arsenide legos are green, but they're really hard to make. Germanium
legos are red, and it turns out that the green Gallium Arsenides fit on them
really well. Yellow Silicon ones, on the other hand, don't fit well with
either.

So that brings us to two. Indium Phosphide legos are blue and so are Gallium
Phosphide legos. But neither of those fit well on the green Gallium Arsenide;
one's lego pins are too dense, the other too sparse. It took a long time for a
manufacturer to come up with the right blend, thickness, and color, but they
were able to come up with a lego that is blue, made from a mix called Indium
Gallium Phosphide, and stacks nicely on top of the green Gallium Arsenide. So
that's 3.

The fourth layer might be Indium Gallium Arsenide Nitride (let's just call it
orange), shoved between the existing layers; somehow making a mix of a good
quality lego, but one that makes the right color, right thickness, and right
pin pitch.

Now to translate to real physics: The pin pitch is the lattice parameter of
each of these crystals, or the distance between individual atoms. If you
attempt to epitaxially grow (grow on top of in the same fashion) a different
compound than what already exists there, it tends to work ok if the lattice
parameters are close. If they're radically different, you can get growth but
it's highly disordered and ends up making a lousy layer and a lousy solar
cell.

------
cauthonLuck
recent improvements in all solid state dye-sensitized solar cells show more
potential for lowering the cost of solar energy.

------
marcfawzi
When will the world run out of the "III-V semiconductor materials" ? And which
nation or corporation currently controls the largest deposits?

~~~
diydsp
haha a legit question, but i guess you got downvoted because you could have
researched it and shared it? dunno.

anyway. not a chem dude at all, but it appears III-V semis are when you
combine: "III-V compound semiconductors obtained by combining group III
elements (essentially Al, Ga, In) with group V elements (essentially N, P ,
As, Sb). This gives us 12 possible combinations; the most important ones are
probably GaAs, InP GaP and GaN." [1]

In other words, the materials in general are: Nitrogen, Phosphorus, Antimony,
Arsenic, Bismuth, Boron, Aluminum, Gallium, Indium and Thallium.

I imagine nitrogen, phosphorus and aluminum are the easiest to find generally
throughout the world.

China appears to control 90% of antimony [2] and its price seems to have gone
up 700% over the last decade.

Arsenic seems to have major supply issues, one of the most critical in terms
of scarcity according to [3] and [4]. Nevertheless, the price has gone down
over the last 100 years significantly and according to this source is less
scarce than it was a century ago: [5]

Bismuth is "relatively rare" but doesn't appear to be scarce. it is found
mostly in Peru Japan Mexico, Canada, Bolivia and not in the USA. [6]

remaining elements are left as an exercise to the reader.

[1] [http://www.tf.uni-
kiel.de/matwis/amat/semitech_en/kap_2/back...](http://www.tf.uni-
kiel.de/matwis/amat/semitech_en/kap_2/backbone/r2_3_1.html)
[2][http://www.tf.uni-
kiel.de/matwis/amat/semitech_en/kap_2/back...](http://www.tf.uni-
kiel.de/matwis/amat/semitech_en/kap_2/backbone/r2_3_1.html)
[3][http://www.acs.org/content/acs/en/pressroom/presspacs/2012/a...](http://www.acs.org/content/acs/en/pressroom/presspacs/2012/acs-
presspac-february-8-2012/arsenic-criticality-poses-concern-for-modern-
technology.html) [4][http://environment.yale.edu/news/article/arsenic-supply-
at-r...](http://environment.yale.edu/news/article/arsenic-supply-at-risk/)
[5][http://theunbrokenwindow.com/2010/03/08/running-out-of-
resou...](http://theunbrokenwindow.com/2010/03/08/running-out-of-resources-
arsenic-edition/)
[6][http://www.carondelet.pvt.k12.ca.us/Family/Science/Nitrogen/...](http://www.carondelet.pvt.k12.ca.us/Family/Science/Nitrogen/bismuth.html)

