“Flower Power”: Photovoltaic Cells Replicate Rose Petals

[OKIsItJustMe]

http://www.kit.edu/kit/english/pi_2016_097_flower-power-photovoltaic-cells-replicate-rose-petals.php

[font face=Serif]Press Release 097/2016
[font size=5]“Flower Power”: Photovoltaic Cells Replicate Rose Petals[/font]

[font size=4]KIT scientists increase the efficiency of solar cells by replicating the structure of petals – publication in Advanced Optical Materials[/font]

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[font size=1]Biomimetics: The epidermis of a rose petal is replicated in a transparent layer which is then integrated into the front of a solar cell. (Illustration: Guillaume Gomard, KIT)[/font][/center]

[font size=4]With a surface resembling that of plants, solar cells improve light-harvesting and thus generate more power. Scientists of KIT (Karlsruhe Institute of Technology) reproduced the epidermal cells of rose petals that have particularly good antireflection properties and integrated the transparent replicas into an organic solar cell. This resulted in a relative efficiency gain of twelve percent. An article on this subject has been published recently in the Advanced Optical Materials journal (DOI: 10.1002/adom.201600046).[/font]

[font size=3]Photovoltaics works in a similar way as the photosynthesis of plants. Light energy is absorbed and converted into a different form of energy. In this process, it is important to use a possibly large portion of the sun's light spectrum and to trap the light from various incidence angles as the angle changes with the sun’s position. Plants have this capability as a result of a long evolution process – reason enough for photovoltaics researchers to look closely at nature when developing solar cells with a broad absorption spectrum and a high incidence angle tolerance.

Scientists at the KIT and the ZSW (Center for Solar Energy and Hydrogen Research Baden-Württemberg) now suggest in their article published in the Advanced Optical Materials journal to replicate the outermost tissue of the petals of higher plants, the so-called epidermis, in a transparent layer and integrate that layer into the front of solar cells in order to increase their efficiency.

First, the researchers at the Light Technology Institute (LTI), the Institute of Microstructure Technology (IMT), the Institute of Applied Physics (APH), and the Zoological Institute (ZOO) of KIT as well as their colleagues from the ZSW investigated the optical properties, and above all, the antireflection effect of the epidermal cells of different plant species. These properties are particularly pronounced in rose petals where they provide stronger color contrasts and thus increase the chance of pollination. As the scientists found out under the electron microscope, the epidermis of rose petals consists of a disorganized arrangement of densely packed microstructures, with additional ribs formed by randomly positioned nanostructures.

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[NNadir]

1. The text from the experimental data from the paper:

Zinc oxide (ZnO) nanoparticles dispersed in isopropanol (1.0 wt%; Nanograde Ltd.) were spun (4000 rpm, 30 s) and subsequently baked (80 °C, 10 min), resulting in a layer thickness of 35 nm. For the active layer, poly[[2,6′-4,8-di(5-ethylhexylthienyl)benzo[1,2-b;3,3-b]dithiophene][3-fluoro-2[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]] (PTB7-Th, 1-Material Inc.) and [6,6]-phenyl C71-butyric acid methyl ester (PC71BM; Solenne 99%) were dissolved separately in o-xylene at a concentration of 20 g L−1 and mixed at a 2:3 polymer:fullerene ratio (w/w). Then, 2 vol% p-anisealdehyde (AA, 98%) were added.[38] The solution was kept at 85 °C before spin-coating. To avoid fast cooling of the solution during spin-coating, the substrates were heated to the same temperature before they were transferred to the spin-coater chuck. The solution was spun (2000 rpm, 60 s), and the samples were then annealed in a vacuum oven (65 °C, 20 min), yielding a layer thickness of 100 ± 10 nm.

Likewise, the infrared absorbing polymer, poly[2,7-(5,5-bis-(3,7-dimethyloctyl)-5H-dithieno[3,2-b:2′,3′-d]pyran)-alt-4,7-(5,6-difluoro-2,1,3-benzothia diazole)] (PDTP-DFBT, 1-Material) and [6,6]-phenyl C61-butyric acid methyl ester (PC61BM; Solenne 99%) were dissolved separately in o-xylene with a concentration of 28 g L−1 and mixed at a 2:3 ratio (w/w). Then, 1 vol% AA was added. Before spin-coating, the temperature of the solution was kept constant (60 °C). The substrates were not heated before spin-coating. The solution was spun on the ZnO layer (1200 rpm, 60 s), resulting in a layer thickness of 100 ± 10 nm.

10 nm of molybdenum oxide (MoOx) and 100 nm of silver (Ag) were thermally evaporated through a shadow mask to form the opaque back contact. The solar cells thus produced possessed active areas with dimensions of 3.5 × 3 mm2. For each configuration, eight solar cells were fabricated, resulting in 42 working devices in total.

Yeah, this looks like an industrial process that can be quickly scaled up much better than the last half a century of "solar breakthroughs" that somehow did very little to have prevented the rise recorded on June 16, of 2016 in atmospheric carbon dioxide of 3.88 ppm over same date of last year

This "amazing" experiment produced current of 15.1 +/- mA per square cm.

If one could imagine that we could find enough indium on the planet to build more of this stuff, and plenty of places to dump o-xylene waste, well, the planet could be saved!!!!!!

If one has ever been in a large scale fine chemical plant, one might wonder about the logistics of synthesizing tens of millions of tons of poly[[2,6′-4,8-di(5-ethylhexylthienyl)benzo[1,2-b;3,3-b]dithiophene but don't worry be happy.

The renewable energy industry is just doing great at making us think we're interested in doing something about climate change, even if our approach consists of large deposits of mindless wishing thinking.

It's too bad that we haven't found a way to convert mindless wishful thinking into results