This is Science: Simple and Cheap Solar Energy



At the beginning of July 2013, one remarkable article was published in the journal Nature, the material of which once again proves that there should be cheap and simple solar energy, and, moreover, this is a matter for the near future.



Back in 1988, a young man named Michael Grätzel ), now a professor at the Lausanne Polytechnic School (EPFL, Switzerland), together with Brian O'Regan (Brian O'Regan) at that time suggested an absolutely crazy idea, namely, to use dyes in solar panels to absorb light and transfer absorbed energy to semiconductor (subsequently titanium dioxide). After that, the electron “moves” along the semiconductor until it reaches the anode, and the dye remaining without the electron (essentially a “hole”, in terms of semiconductors) receives it from I - ions , which, in turn, turn into I 3– ions (the so-called redox vapor), transferring charge to the cathode. As a result, there is some useful potential difference at the two contacts. Over time, such cells became known as Gratzel cells or Dye-sensitized solar cell , DSSC (dye sensitized / activated solar cells).


DSSC Principle of Operation ( Source )

And everything would be fine, if not one BUT. From the point of view of physical and chemical laws, the efficiency of such a battery cannot exceed 33% - and even then, only in theory. The only advantage of this kind of solar cells is their fabulously low cost of production compared to silicon, for example. It is worth recalling that in 1991, the world was completely ruled by faith in silicon for terrestrial applications (including the nascent class of thin-film technologies) and gallium arsenide (GaAs) for space.


Data collected by the National Institute of Renewable Energy (USA)
It took 25 years of truly titanic efforts (for a long time it was not possible to exceed the threshold of 10%), so that 5-6% of the efficiency of converting solar energy into electricity turned into almost 15%!

The essence of the perfect discovery is the use of a polycrystalline perovskite-like compound of lead - CH 3 NH 3 PbI 3 - as a sensitizer and mediator (conductor of "holes"). This material is actually chemically deposited — it does not require vacuum installations — on the surface of mesoporous titanium dioxide (“balls” in the micrograph). The resulting layered cake has a thickness of about 1 micrometer (~ 50-100 times thinner than a human hair) and when encapsulated, it is usually clamped between two thicker plates of glass:


Microstructure DSSC: HTM (organic hole-transport materials) - material that conducts holes well, FTO (fluorine-doped tin oxide) - fluorine doped tin oxide, which plays the role of a transparent conductive electrode .

But the current-voltage characteristic of the device is impressive:
PCE ( Power Conversion Efficiency ) or energy conversion efficiency has reached 15%! This is a truly significant event in the solar industry, for which, incidentally, Michael Gratzel will be awarded one of the most prestigious prizes in November this year - the Marcel Benoist Prize , among 9 award-winning Nobel laureates.

By the way, for reference. In 2009, Gratzel launched the semi-industrial production of DSSC batteries ( for fans of the iPad , for example). And, according to rumors, in Lausanne it is planned to install new highly efficient batteries on the roof of the palace of justice ...
Links:
1. Publication of the previous work in the public domain.
2. Article in Nature.



Full list of published articles by This is Science on GeekTimes:
This is Science: Simple and Cheap Solar Energy
This is Science: Graphene - Life or Death?
This is Science: Blow and Get Electricity
This is Science: Silicon Electronics: Bend Me All the Way!
This is Science: An elastic display on quantum dots.
This is Science: Putting triboelectricity at the service of humanity.
This is Science: 3D optical printing moves to the micro level.
This is Science: What's inside a neuromorphic chip?
This is Science: News from Graphene Fields
This is Science: 3D electronic lithography to the masses
This is Science: Discharge of alkaline batteries or why the battery bounces
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This is Science: wearable electronics and triboelectricity. Part 1
This is Science: Wearable Electronics and Triboelectricity. Part 2


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