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Hybrid solar cells show a transcendent performance


Developed at the University of Cambridge (UK) new photovoltaic cells are able to raise the quantum efficiency of solar cells on a whole new level. According to scientists from the group of Sir Richard Friend and Neil Grinhama, internal quantum efficiency of their hybrid battery reaches an incredible value at 50%.
If you have not yet penetrated the greatness of the moment (“Where’s the other half?”), Let us note that, according to the physics of solar cells based on silicon (pn specification defines the width of the transition zone in the semiconductor), there is a limit of maximum quantum efficiency is 33 , 7% (Shockley-Queisser limit). You may reply to this is that the value is valid only for a single pn zone, and if the layers in an infinite number of battery, the indicator will rush to 86%. This is true, but in the real world, of course, and worst of all is that the way of progress is always worth the price. Because producers are more interested in the price tag on a product, do not increase the number of layers, and reduce. But efficiency is necessary to solve the problem by some other means, and as a result of record numbers of quantum efficiency does not exceed 25%, and it is considered an unconditional victory and can be optimistic about the future of zealots “green” energy.
Eminent scholars, Physics Department, University of Cambridge, and Sir Neil Grinhamu Richard Friend is no stranger to live and work under the motto «Think different». Using the accumulated knowledge in optoelectronics, nanomaterials and organic conductors, they have managed to develop a new type of hybrid solar cells.
Conventional batteries can absorb only a part of the solar light, and larger part of the light energy (especially high-energy photons of blue spectrum) is lost as heat. It is the failure of traditional solar cells absorb photons of any wavelength in the range from near UV to near IR is one of the reasons that the limit Schottky – Kvizera in 34% of the light energy is available to us.


Hybrid batteries are able not only to successfully absorb red light, using layers of nanoparticles of lead sulfide (PbS), but get to photons in the visible spectrum (including blue) more energy, dramatically increasing the flow of electricity output. Usually solar cell produces one electron per absorbed photon is useful. But in a hybrid solution by using pentacene (organic semiconductor that absorbs visible light, including blue region of the spectrum, but because he is very black) and features of the interface between the inorganic and organic material PbS pentacene, is a generation of two electrons per absorbed photon high energy (visible light, including blue area).

Thus, the hybrid material produces about twice as much electricity from visible light, including blue, and simultaneously converts photons, even with the lowest energy (IR). All together, this makes it possible to catch up to an unprecedented level of internal quantum efficiency of 50% of the available solar energy.
And a few words about the shortcomings of the proposed solution, in which the authors, of course, yet ignore. First (and second, and so on), it is pentacene, that is a bright representative of polycyclic aromatic hydrocarbons. If so, then this is a very strong carcinogen, mutagen and teratogen simultaneously. Large-scale production (you can allocate from the oil, but there is not enough at all) involves several stages at each of which the starting materials, the reaction products and by-products – carcinogens, mutagens and teratogens, one steeper than the other. A much needed pentacene. Where and who is going to produce? And also with the synthesis of starting something not … The most simple and affordable starts with benzene derivatives (also a carcinogen, and even flying), but the most important thing is that the main source of benzene – is crude oil. Scare us: oil is over, and then the solar power (along with other alternatives) will be your salvation. Maybe, but not one that is tied to the use of aromatic organics. So, independent of the silicon oil, though, and now looks ugly duckling compared to the organic / inorganic hybrid, tomorrow will be indispensable because of its independence from oil. Finally, the pentacene is very prone to oxidation by atmospheric oxygen under UV irradiation (singlet oxygen oxidation of conjugated systems). Where, if not in the solar cell, will meet with pentacene, oxygen and UV sunlight! Hence, a hybrid battery life based on pentacene is very big doubts, as it may protect.