Nanosolar is the next Solyndra

Book of Synergy

These cells are also under the name Dye solar cells (DSC) or Dye-sensitized solar cells(DSSC), i.e. dye or dye-sensitized solar cells.

The technology, which is one of the most interesting contemporary developments in the field of photovoltaics, will be presented for the first time 1991 internationally known under the name of its inventor, the German chemist Michael Graetzel. Together with the American researcher Brian O’Regan at the Institute for Physical Chemistry of the Federal Technical University of Lausanne (EPFL) 1988 The photo-electrochemical technology developed is not new, but has now been made efficient for the first time. The solar cell works with non-toxic Titanium dioxide, achieves an efficiency between 8% and 12% and is very cheap to manufacture. Another special feature is their sensitivity to diffuse light: If, for example, 10% is achieved with direct sunlight, the efficiency - in contrast to all other types of solar cells - even increases when it is cloudy or the air is very sandy and can then reach up to 13%. Based on endurance tests, a shelf life of up to 5 years without a drop in performance is already assumed.

This breakthrough was so serious at the beginning of the 1990s that the researchers initially only met with skepticism and mockery.

The functional principle of the cell is similar to the effect of chlorophyll in the process of photosynthesis. In the Grätzel cell, the electrons of a wafer-thin layer of dye are excited by the incident sunlight and then flow through a semiconductor layer made of titanium dioxide into the conductor layer attached to the glass. The dye itself compensates for its charge deficit with electrons from an overlying layer of iodine solution. Titanium oxide is mass-produced and cheaply produced as a white paint and addition to toothpastes, and it proves to be very durable even with long-term exposure to radiation.

It is true that Prof. Helmut Tributsch from Berlin is making an effort Hahn Meitner Institute as well as a Japanese research group since 1970s Years to develop an efficient photoelectrochemical cell, but so far without success. At the time, the Japanese reported that they could split water into hydrogen and oxygen using light and the semiconductor titanium dioxide. However, the yield was extremely low, since the titanium oxide (alone) can only use the ultraviolet part of the sunlight. The German physical chemist Heinz Gerischer also had the beginning 1970s Years tried to sensitize semiconductors by means of dissolved dyes, but the drive energy fizzled out after 10 - 100 billionths of a second. And despite the surface binding of the dyes, a dense layer only absorbed about 1% of the incident light.

The problems that these scientists failed to solve are explained by Grätzel, who since 1976 researching first in Berkeley and then in Lausanne, ingeniously solved: The coupling of the titanium oxide with a dye sensitizes the cell for a much broader spectrum, the light yield is increased by the roughening and the accompanying enlargement of the surface by 1,000 times A particularly stable metal compound is selected (which can be found in every hardware store), and the otherwise so frequently observed and destructive bubble formation is suppressed by a solution with a boiling point of over 200 ° C.

The Swedish-Swiss electrical company Asea Brown Bovery (ABB) is interested and wants to test whether the cell can also be produced in large numbers - but only with 'braked power', as ABB expresses itself surprisingly openly. The Swiss chemical company Sandoz meanwhile is working on optimizing the dye. In the year 1992 At least Grätzel reckons that the first cells will come onto the market in two years, at a price of around $ 2 / W - that is, less than half the price of the currently cheapest cells.

I myself hear about this innovation quite early on and correspond with other interested people about it, so that I already 1992 a personal, handwritten test report is available in which the artist Ariane Ritter from Nuremberg sent a very detailed description of her work, how she made a small, very simply structured dye cell by hand in her oven at home - which actually works.

After the Book of Synergy Martin Löffler contacts me, who would like to repeat Ariane's attempt. He also types up Ariane's letter so that I can publish the technical part here:

I can no longer fully understand the attempt to build a solar cell with 2 colors that contain metal, because I can only think of one of the colors used.

Nevertheless, I will describe the experiment as clearly and clearly as possible.


    • Aluminum foil (as carrier material)
    • Gelatin sheets (or powder)
    • An orange pigment

I put a layer of gelatin on a piece of aluminum foil approx. 20 x 20 cm and let it dry. Then I applied 2 color fields that shouldn't touch. The color fields consist of gelatine dissolved with water and color pigment that contains metal. I dried the color pigment layer in the oven at 50 ° C.

After this drying process, no voltage could be measured between the two color fields. After approx. 4 hours of strong sunlight, a clear tension could be read between the color fields.

So much for the attempt. I hope I have helped you a little. You should now find a specialist who simulates the attempt to find out the other metal-containing color pigment and find a way to convert the voltage into electricity. (...)

Of course, this do-it-yourself solar cell does not achieve any level of efficiency worth mentioning, but what fascinates me so much about the principle of the dye cell is its approach to technological democratization of photovoltaicsas I like to call it.

Because all other solar cells require extremely complex, technically complex and very expensive systems for their production. Both these systems and the infrastructure required for them are assigned to the high-tech sector and are therefore largely a monopoly of large companies in technologically advanced industrialized countries. They also require highly qualified employees. In third world countries, on the other hand, the implementation of the necessary clean room technology for the production of silicon is as good as impossible - even if the whole country is otherwise almost entirely made of sand ...

With the Gräzel cell, everything looks a little different for the first time. If someone in Germany can 'bake' such a cell himself in his kitchen, then someone in Mongolia, Mauritania or Malta can just as well do it. So read along again: In contrast to all other types of solar cells, the production of the Grätzel cell is almost as easy as preparing a sandwich: You coat a tin oxide-coated glass pane with titanium oxide, roast the whole thing in the oven for half an hour, then coat it A 'toast slice' with a dye, an iodine solution on top, a second steamed glass plate on top - and the solar cell is ready!

While the average efficiency of the (advanced) Grätzel cell in December 1991 is still 10.4%, it reaches the end 1992 almost the 15% mark. center 1993 production readiness is announced, and 1994 one learns that the first products with Grätzel cells are to come onto the market. Modules for higher performance could go into series production in just a few years. According to an estimate by the American Triangle Research Institute in North Carolina, the cell will cost only a fifth to a tenth of what is currently estimated for the other cells on the market in industrial production.

A good friend, the journalist Leila Dregger, informed me in January 1996 about her meeting with Graetzel. She also allows me to present her report here:

“(Grätzel) himself is of course always enthusiastic about himself. It was funny at all, an interview during a S-Bahn ride from Wannsee to Lichtenberg, sightseeing in Berlin and so on in between. A really lovable absent-minded professor. Yes, he is from Berlin, but now lives and works in Lausanne.

The Grätzel cell consists of a semiconductor film that is only a few ten thousandths of a millimeter thick and into which tiny depressions are incorporated. This "spongy" semiconductor layer is coated with a (red) dye that absorbs sunlight. Low manufacturing and material costs, the cheap and widely used raw materials are glass, titanium dioxide (white color pigment), organic solvents e.g. iodine.

The system is now being researched further at the Institute for Applied Photovoltaics in Gelsenkirchen until it is ready for practical use. People hope to be able to compete with conventional power generation in three to five years. A first solution was found for the short service life (two instead of at least 20 years): sealing with liquid gas so that no water penetrates the cells. But there is also a high susceptibility of the organic compounds to adhesives. And the efficiency is not bad at all, almost 10%, but also with diffuse light. For this cheap production, and because you can make it almost transparent and therefore also use it as a window, that's a great thing. So far, however, you cannot interconnect them, i.e. combine them to form large systems. They want to solve this by the year 2000.

But there are two tinkerers in Switzerland, the Meyer twins, who have already solved the problems in the kitchen. Instead of metal interconnections, which are always eaten away by the iodine compound, they use carbon. The two Meyer seem to be really fit and personable, real hobbyists who don't care too much about a problem.

Grätzel research funds? Little I would not mention: Nine million DM for the first development step, paid by the state of North Rhine-Westphalia (80%), the Rheinische and Hamburgische E-Werken, the Gelsenkirchener Flachglas GmbH, the Essen specialty chemicals manufacturer Thomas Goldschmidt, the municipal utilities and the science park Gelsenkirchen.

Goal: 10 sqm modules with 10% efficiency by the end of 1996.
Prices: from 30 to 40 Pf / kWh in 3 to 5 years.

The application remains for small, fine things, especially indoors. So calculators, batteries and clocks. Swatch is launching the first Grätzel watch this year. A bathroom scale should come onto the market in Switzerland as early as 1994. "

Beginning 1995 the Berlin HMI names the haptic problems of the Grätzel cell: Its efficiency reaches only 8% and the cell is not stable in operation. Lausanne then reports that through the implementation of an 'anchor molecule' containing a light-active ruthenium complex, 10 % can be achieved. The Institute for applied photovoltaics GmbH in Gelsenkirchen, a partner of Graetzel, assumes that it will be able to compete with conventional electricity generation in three to five years, even if the service life has to be increased from the current 2 years to at least 20 years.

1996 the Grätzel cell already achieves an efficiency of 18 %. For the company Solaronix In Aubonne (see below), in the canton of Vaud, the above-mentioned Meyer brothers Andreas and Tobias are developing a construction kit that students and others can use to produce cells of this type themselves; marketing is scheduled for autumn 1997 start. center 1998 in the press, however, is still of a shelf life of only one year and an efficiency of 8 % spoken. In Gelsenkirchen, they calculate with it 2000 with the pilot production of the nano-structured dye-sensitized solar cells, as they are called in official parlance, to be able to begin. end 1998 Grätzel also announces the development of a solid solar cell that uses a new organic substance called OMeTAD works - and an efficiency of up to 33 % should have. Mainzer is part of this development Max Planck Institute for Polymer Research involved.

end 2004 should the Grätzel cell from the company Konarka Technologies from Lowell, Massachusetts, which works together with the American research laboratory in Oak Ridge, can be brought onto the market under the name nano solar cell (s.d.) after a corresponding solar cell layer has been successfully applied to a curved surface (e.g. car body). At this point in time, 100 W should be harvested per square meter.

Toyota presents as early as March 2005 the first building with facade-integrated dye cell collectors, a prototype named Dream House, which, in addition to advanced solar technology, also serves as a presentation object for future home automation technology that the company is targeting 2010 expected to market. As the first manufacturer comes in the year 2006 the Company Peccel, a Yokohama University spin-off with their Dye-sensitized cell as a series model on the market.

The EPFL licensee Konarka Technologies, who meanwhile has its product Dye-sensitized solar cell (DSSC), signed in August 2006 with London-based Renewable Capital Ltd. a cooperation agreement for large-scale industrial production of his Power plastic Cells ligaments. The company has greatly developed the original Grätzel cell and also designed a production technology for inexpensive manufacture. A photovoltaic nanotechnology is used here, with which tiny particles - 1000 times smaller than the diameter of a human hair - are applied to plastic or fiber materials.

Power Plastic from Konarka

Konarka's European headquarters are in Nuremberg, and there are research centers in Austria and Switzerland. The company is also promoting its ability to offer camouflage-colored films for military applications. In September 2006 The press reports that Konarka is planning a 20 MW manufacturing facility for foil-based Graetzel cells. (More about Konarka can be found under organic solar cells).

Michael Grätzel meanwhile continues to teach at the Swiss Federal Polytechnic in Lausanne and is also working on the use of Nanocrystalsin order to significantly increase the efficiency of his cells again. In the new light harvesting systems, hundreds of Nanoparticlesthat are coated with a dye that absorbs the light, with the nanoparticles themselves transporting the electrons. Below I will speak again about the nano cells.

Camouflage-colored solar roof
from Konarka

Craig Grimes and his team from the Pennsylvania State University present in February 2006 Solar cells made up of tiny tubes Titanium dioxide consist. These act like expressways for electrons and thus increase the electricity yield. The solar cells are manufactured by first applying a transparent electrode layer and then a 500 nanometer thin layer of titanium to a pane of glass. The glass is then immersed in an acid bath while an electric current flows at the same time, as a result of which the titanium is oxidized and tubes of titanium dioxide up to 360 nanometers long grow in the titanium layer.After it has crystallized out, the titanium dioxide is treated with a dye, followed by an iodine-based liquid electrolyte and, finally, a counter electrode.

As soon as light falls through the gas plate, the dye releases electrons, which are quickly channeled through the nanotubes to the negative electrode. From there they can get to the positive electrode via a circuit and through the electrolyte back to the dye - doing electrical work in the process. There is now plenty of need for optimization, because with the 360 ​​nm long nanotubes, the efficiency of the dye-sensitized solar cells is only around 3 %. This value is to be increased by using tubes several thousand nanometers long and by reducing the distance between the two electrodes. The theoretical ideal value is at least 31 %and it is associated with a relatively simple and commercially feasible fabrication. You can find out more about nano cells below and in the chapter on optimization and amplification techniques.

In December 2006 are available to researchers from the Institute for Physical Chemistry and Electrochemistry Leibniz University Hannover shortly before the commercial introduction of an inexpensive dye solar cell developed there, in which the Titanium dioxide and Zinc oxide layers be electrochemically deposited or applied as a porous film on a conductive substrate. A dye is deposited on this oxide layer, in the molecules of which electrons are excited by sunlight, which are transferred to the semiconductor oxide and diffuse to the conductive back contact. The researchers are working on lowering the production temperature of the cells to room temperature, and they have also set themselves the goal of developing flexible dye solar cells that can be integrated into clothing or tent tarpaulins, for example. These should also be produced in many bright colors in order to make them more popular as energy-generating accessories.

In January 2008 reportedly from the Swiss team Ecole Polytechnique Federale de Lausannethat a solvent-free DSSC cell has been made that is based on a binary ionic liquid electrolyte based. With an efficiency of 7,6 % a new record is measured. In addition, the cell is stable for over 1,000 hours at 80 ° C in the dark or at 60 ° C when exposed to light.

The dye molecules fixed on titanium dioxide electrodes have proven to be a very attractive cell variant, which combine low costs and relatively simple production with a high degree of efficiency. The 11% that has already been partially achieved, however, only affect cells that use volatile organic solvents as electrolytes, which makes their practical use very difficult due to the high vapor pressure of these solvents.

Michael Graetzel, Shaik Zakeeruddin and their colleagues use a mixture of two ionic liquids as a redox electrolyte in conjunction with a new type to manufacture this solvent-free solar cell Ruthenium-based dye. Ionic liquids essentially have a vapor pressure of zero, which is why they are to be preferred even to stable and non-volatile organic solvents.

In the meantime there is a very detailed and highly recommended self-assembly guide for the University of Bayreuth.

But many other groups are already working with dye cell technology:

end 2006 announce scientists of the University of Tor Vergata in Rome the development of a new type of dye cell in which the pigment of Blueberries is being used. The dark dye called Anthocyanin When it comes to the spectral absorption of sunlight, most of the other vegetable dyes stand out, although the efficiency has only yet been achieved 1 % amounts.

A cost reduction of 90% compared to silicon cells promise in April 2007 novel green dye cells from New Zealand, which also implement diffuse light well. For this is synthetic chlorophyll whose molecules are applied to a thin film of interconnected titanium dioxide particles that, like nano-tubes, transmit the electrons set in motion by the incident light on the dye. Basically, it is also possible to turn it into a coat of paint that then generates electricity. The more than 10 years of research at the Massey University in Auckland were funded by the Foundation for Research, Science and Technology. The first Green-Dye dye cells should be during the year 2008 come on the market.

In May 2007 report George Crabtree from Argonne National Laboratory near Darien and Michael Wasielewski from the Northwestern University Another method of manufacturing a solar cell using very simple basic materials to split water and produce hydrogen. They also use titanium dioxide (see below, hydrogen).

In August 2007 report researchers to the Ohio State University great progress with one pink version of the DSSC cells, whereby for the first time more complex metal compounds and different particle shapes are used to increase the yield. The pink arises because red Ruthenium compounds mixed with white metal oxide powders, mostly titanium oxide or zinc oxide. In addition, zinc stannates are used, more complex oxides whose properties can be controlled more specifically. With these, the solar cells achieve an efficiency of 3,8 %, a quarter of the yield of typical silicon cells. But already 2006 a DSSC variant had been developed here, the titanium oxide of which was in the form of tiny nanowires, which meant that the electron transport was more direct and the cell had an efficiency of 8,6 % reached. Now they are working on the construction of tree-shaped nanowires in order to be able to conduct the electrons even better. In this DSSC design, the particles enveloped by the dye are supposed to provide the surface like leaves, while the nanotrees branch out between them to transport the electrons. However, it is only expected to be ready for the market in a few years.

Prof. Arie Zaban from the Israeli Bar-Ilan University developed and patented together with specialists from his company Bar-Ilan Nanotechnology a solar cell in September 2007 is presented, and those from a few nanometers in diameter Nanodots consists of platinum and metal wires on electrically conductive glass. This type of cell is up to an area of ​​100 cm2 manufacturable. Using nanotechnological means, a sponge-like network of nanodots is applied to a flexible plastic carrier, with the semiconductor material used being filled with an organic dye that absorbs the light energy. In addition, a method is being developed to reduce the consumption of platinum in cell production by a factor of 40. In December 2007 a cell measuring 10 x 10 cm is already presented.

Zaban is also a consultant to the company Orionsolar Photovoltaics Ltd. in Jerusalem (not to be confused with the Australian Orion Solar Pty Ltd.), which wants to promote the commercialization of the new solar cells as part of a partnership with Bar-Ilan University. It is hoped to be ready for the market within the next five years. Beginning 2008 The company's production technology allows solar cells in the dimensions 15 x 15 cm and with an efficiency of 7 % to manufacture.

In December 2007 presents the Toin University in Yokohama a DSSC cell in A4 format with an efficiency of 6 % having. The university's industrial partners already have a production capacity of 10 MW per month and want to start in February 2008 offer their products for commercial use. One reason there are more and more companies in this sector is the expiry of a number of fundamental patents in the course of the year 2008.

In the year 2008 developed Grätzel together with Satoshi Uchida from the Tokyo University new dyes that contain the nitrogen-containing indoline molecule and are stimulated more effectively by light. Even without ruthenium dye, the cells made from it achieve an efficiency of over 7 %. One shared with Shaik Zakeeruddin and his colleagues on Changchun Institute of Applied Chemistry The cell developed by the Chinese Academy of Sciences, which does not use volatile organic solvents, achieves an efficiency of 8,2 %.

In June 2008 the announcement takes place that at the Saudi King Abdullah University of Science and Technology (KAUST), a center for advanced molecular photovoltaics is to be set up, in which Stanford University and the Ecole Polytechnique Fédérale de Lausanne (EPFL) as well as the industrial partner G24 Innovations will participate. The center is funded by a $ 25 million grant over the next five years.

In November show ruthenium-based cells that Grätzel together with researchers from Chinese Academy of Sciences around Prof. Peng Wang has developed greater stability at high temperatures than all previous models; they retain over 90% of their initial output power even after 1,000 hours in full sunlight and at a temperature of 60 ° C. With an efficiency of 10 % a new world record is also achieved.

For Michael Graetzel himself, the world should be fine by now. 2009 he receives the renowned Balzan Prize, endowed with 1 million Swiss francs, for his groundbreaking invention 2010 the € 800,000 Millennium Technology Prize awarded by Finland, which is also known as the Nobel Prize for Engineers - and whose trophy is, appropriately enough, a pointed silicon crystal. This was preceded by numerous other awards, including in the year 2000 the grand prix européen de l’innovation, 2001 the Faraday Medal, the Gutenberg Research Award and the Dutch Havinga Award, 2002 the IBC Award, 2003 the Italgas Prize, 2005 the Gerish price, 2008 the Harvey Prize and 2009 the Galvani Medal. 2011 is Grätzel with the since 1921 awarded Wilhelm Exner Medal, and 2012 with the Albert Einstein World Award of Science. The chemist, once ridiculed, is now one of the ten most cited chemists in the world.

Michael Graetzel with the
President of the Republic
Tarja Halons

center 2010 the conversion efficiencies of Graetzel's own cells under standard conditions are included 12 % on a laboratory scale and at 8,6 % for modules, and this with a life expectancy of over 25 years. However, there are still further improvements in efficiency up to a maximum 31 % for single cells and above 40 % possible for tandem cells and should also be promoted through intensive research.

The one mentioned G24 Innovations Ltd. (G24i) in Cardiff, Wales, had in November 2007 "After 18 years of research and development" (and the acquisition of the corresponding licenses from Konarka in the previous year) signed their first contract: The extremely light and durable dye sensitized Thin film solar cells (Dye Sensitized Thin Film, DST) of the British company are to be bought from Master IT Ltd. for cell phone chargers in Kenya, pioneering affordable and convenient mobile communication that also reaches some of the poorest sections of society. In December, G24 agreed a cooperation with BASF to develop ionic liquids and dyes in order to further improve the performance and efficiency of solar cells. Ionic liquids are used because they do not volatilize even at higher temperatures.

In June 2008 Morgan Stanley Principal Investments put $ 20 million in G24i, followed by another $ 30 million through 4RAE in July. In September, G24i and the 2005 founded the Dutch company Lemnis Lighting to collaborate on the development of high-performance, solar-powered LED lights for industrialized and developing countries. The companies had received a grant of $ 200,000 from the World Bank as part of the 'Lighting Africa' program. More about this can be found in the subsection Solar lights for the 3rd world.

2009 The G24i begins mass production of flexible modules, and in October the first delivery of DSC modules takes place to the bag and backpack manufacturer Mascotte Industrial Associates in Hong Kong, which integrates the cells into its products. Grätzel congratulates the company on its success. A month later, G24i signs another development agreement with three of China's largest government research institutes. 2010 G24i has a 120 m high wind power plant built by Ecotricity on the factory premises in order to "Making green products with green electricity“To be able to. And Tonino Lamborghini is the first company to bring solar powered bags with DSSC thin film solar cells from G24i to the market.

Solar bag from
Tonino Lamborghini

2011 This is followed by a collaboration with Texas Instruments to implement the DSSC cells in the electronic products of the US group. And in April 2012 G24i announces that its cells with their current, average efficiency of 26 % have broken all previous records. In May, an agreement follows with Logitech to manufacture the world's first light-powered, ultra-thin Bluetooth keyboard, which will start in May 2012 in the US and Europe at a price of about $ 130. The Solar Keyboard Folio, which actually costs € 130 in Germany, is offered as an accessory for the iPad 2 and the third Apple tablet in the manufacturer's online shop. Normal daylight or artificial light is sufficient to charge the built-in battery.

However, the Swiss company calls itself the “leading company in the development of dye solar cells” Solaronix SA, which is based in Aubonne, around 20 km from Lausanne. That is what it is already 1993 Founded company of the twin brothers Andreas and Toby Meyer. In parallel to the development and engineering business, Solaronix produces specialty chemicals such as ruthenium dyes, redox electrolytes and various types of nanocrystalline titanium oxides, as they are mostly used in dye solar cells.

2003 45 x 45 cm cells are being produced here for the first time - and Solaronix is ​​participating in this Full spectrum research project the European Commission, which aims to make better use of the solar spectrum. In addition, a cooperation agreement is signed with the Jerusalem-based company Orionsolar (later: 3GSolar, see below) for the development of low-cost dye cells. 2005 the company becomes a member of the funded by the European Commission Napolyde project, which involves 23 large corporations, small and medium-sized enterprises and academic centers from 11 countries to drive innovation in solar cells.

2010 Solaronix doubles the size of its manufacturing facility and starts selling the first organic dye called Sensidizer SQ2, a squaraine derivative that produces blue to green colored solar cells. [Squaraine is a class of intense dyes based on squaric acid or its esters, and which are therefore also known as squaric acid dyes.] In October, a publication with the title,Dye Solar Cells for Real, The Guide for Making Your Own Solar Cells’Made available for free download (PDF / 8.5 MB / version 2012), in which the manufacturing process of a dye solar cell is described in great detail and easy to imitate.

With the current update of this chapter center 2012 On its homepage, Solaronix offers training kits and (quite expensive) demonstration solar cells along with their electrical accessories (motor, model wind turbine), interconnected dye solar cell modules (Serio) and advanced, completely printed dye solar cell prototype modules ( Mimo).

Via the Israeli company mentioned above 3GSolar Photovoltaics Ltd., which produces highly efficient low-cost DSC modules of the 3rd generation using a simple, cost-effective screen printing process and works closely with Joma International, a leading manufacturer of titanium dioxide (TiO2) nanoparticles with tailor-made properties, there is hardly anything else to find out. Funded by Israel Electric Corporation (IEC) and Smedvig Capital, the company claims to have developed the world's most efficient large DSC without disclosing any figures. 3GSolar is also working on the further development of the so-called Forster Resonance Energy Transfer (FRET) technology, in which quantum dots are intended to further increase the performance of the dye cells - here too, so far without any indication of any values ​​already achieved or planned.

It looks even more active on a scientific level - research and investigation, experimentation and testing is taking place almost everywhere in order to further exploit the potential of DSSC cell technology.

Annemarie Huijser defends in March 2008 at the TU Delft Your doctoral thesis on the implementation of biological processes on solar cells. Plant cells can transport absorbed sunlight over long distances (in proportion), typically 15 to 20 nanometers, to the point where it is converted into chemical energy. This is because the chlorophyll molecules in the leaves are arranged in the best possible sequence. Huijser is therefore concentrating on dye-sensitized solar cells, where the color layer that covers the semiconductor titanium dioxide absorbs the energy from sunlight and thus the so-called Excitons creates, which then have to move in the direction of the semiconductor. She compares dye molecules with Lego bricks and varies the way the bricks are stacked to see how this affects the transport of the excitons through the solar cells. These should move as freely as possible through the cell material in order to generate electricity as efficiently as possible.

Huijser's solar cells are closely related to the Graetzel cells. In these, however, the dye and the semiconductor are very close to each other, they are almost mixed. As a result, the excitons do not have to move far. A disadvantage of this type of cell, however, is the complex method of charge transport connection. For this reason, Huijser takes a different approach and uses a two-layer system of dye and semiconductor. By studying the best Stringing together of the dye molecules succeeds in increasing the mean distance that the excitons move in the solar cell by twenty times - up to a distance of approx. 20 nanometers, which corresponds roughly to the systems found in nature. In order to make this new type of solar cell economical, the mobility of the excitons must be increased by a factor of three, which, according to Huijser, is quite possible.

In April 2008 report researchers led by Prof. Guozhong Cao at the University of Washington an almost dramatic improvement in dye solar cells, which they were able to achieve through an internal structure that is reminiscent of popcorn. With the tiny grains of around 15 nanometers in diameter of the semiconductor layer, which clump together to form larger spheres of around 300 nanometers in diameter, a surface area of ​​almost 100 m is created2 per gram of material. The dye molecules sit on it, from which the light releases electrons, which then migrate into the semiconducting granule layer and lead to the flow of current. For simple little grains out zinc oxide the researchers went from 2,4 % Efficiency off - but totally unexpectedly achieve an efficiency of with the popcorn ball design of the same material 6,2 %. Since this porous structure holds the incident light longer, the efficiency of the cells has more than doubled!

While the scientists are carrying out their first experiments with the easy-to-use but chemically unstable zinc oxide, the more efficient titanium oxide will be used in the next few experiments in order to increase its values ​​as much as possible. The research is funded by the National Science Foundation, the Department of Energy, the Washington Technology Center, and the Air Force Office of Scientific Research.

Students of the Rowan University in Glassboro, New Jersey, will present in May 2008 Solar cells that they made with the coloring agents of blackberries, blueberries, oranges and grapes. The team around Prof. Darius Kuciauskas is independently developing a process for extracting the dyes. Here, the heavy particles are separated with the help of filters and a centrifuge in order to obtain a liquid that is dry-frozen. What remains are sugar and coloring matter, after which a pure, light colored coloring matter remains in an acidic solution after their separation. These organic solar cells have a low output, but the production of color from fruit is dirt cheap.

In June 2008 the message follows that the use of Nanotubes can increase the performance of DSSC thin-film films by ten times. Jessika Trancik from Santa Fe Institute, Scott Calabrese Barton of the Michigan State University and James Hone of the Columbia University use carbon nanotubes to create a single layer that performs the functions of both the oxide and platinum layers - requiring three properties: transparency, conductivity and catalytic activity.

Dye solar cells currently have a transparent film made of an oxide that is applied to glass and is electrically conductive. An additional, separate foil made of platinum acts as a catalyst to accelerate the chemical reactions involved. However, both materials have disadvantages: the oxide layers cannot simply be applied to flexible materials because they work significantly better on a rigid and heat-resistant substrate such as glass, while expensive equipment is required for the production of the platinum foils.

Ordinary films made from carbon nanotubes also have a problem: If the film is made thicker in order to be a better catalyst, it becomes less transparent. Based on the theory that materials function better as catalysts when they have tiny defects, the researchers expose the carbon nanotubes to ozone, which roughen them a little - and suddenly turns very thin films into much better catalysts, the effectiveness of which is that of platinum comes close.

In the year 2008 reach the cells of the year 2004 in Queanbeyan, Australia, near Canberra (state of New South Wales) Dyesol Ltd. a peak efficiency of more than 11 %. and describes itself as a "world leader" in dye solar cells. The company intends to commercialize the dye solar cell technology that was developed by Sustainable Technologies International, Greatcell Solar and EPFL in Switzerland over the course of the previous 14 years and becomes a pioneering licensee of DSC technology. The founding team already had in 2000 the world's first prototype production line for DSC cells started.

From 2005 is following Dyesol's strategy of accelerating the development of DSC through partnerships with industrial giants in key markets. These include Corus in Great Britain (formerly British Steel), which are used to develop DSC on strip steel produced on coil coating lines, and Pilkington, which is working on DSC glass elements for integration in buildings. Further partnerships and projects lead to prototypes such as the flexible multi-cell film SureVolt for camouflage and security applications by the Australian Department of Defense.

2009 Dyesol signs cooperation agreements with Merck for the development of novel electrolytes for higher DSC performance, and with the Australian CSIRO for the development of dyes that are more effective in collecting energy and more stable in long-term use. Dyesol now supplies third generation manufacturing, prototyping and research equipment, and the Australian manufacturing facility has the capacity to grow up to 200,000 m per year2 To produce DSC products. The production lines currently produce ocher-colored dye solar cells, but the company plans to offer cells in gray, green and blue in the future.

Solar cell window
from Dyesol

In February 2010 Dyesol founds a GmbH in Bavaria as a subsidiary, and in May Singapore Aerospace Manufacturing Pte. Ltd. signed a memorandum of understanding to jointly establish an automated pilot manufacturing facility for DSC cells with an annual production capacity of more than 20,000 m2 to design and build. In July, the two-year research project carried out with the project partner Corus will be completed, which concerned a technique for applying dye solar cells to steel strip on an industrial scale. And in November, a cooperation agreement for a joint three-year program will be concluded with the Japanese National Institute for Materials Science (NIMS) in order to further increase the efficiency level of dye solar cells.

In the year 2012 Dyesol Inc., the US subsidiary of Dyesol Ltd., is working on the market entry in the field of building-integrated photovoltaics (BIPV) - with 120 x 60 cm DSC glass modules. Dyesol Inc. also owns 50% of the Ohio-registered joint venture company DyeTec Solar, which is to market the BIPV glass products. One already 2008 with Timo Technologies Co. Ltd. Joint venture founded in South Korea under the name Dyesol-Timo supplies the DSC modules, which are highly innovative in terms of style, for the in March 2012 installed in the Human Resource Development Center in Seoul City and produced by the Korean glass manufacturing company Eagon Industrial Co. Ltd. manufactured windows. They are modern stained glass windows that generate clean, renewable electricity from sunlight. At the Industry Awards 2012 of the Australian Clean Energy Council, Dyesol is the winner of the newly created innovation award.

Since many textile outdoor products such as awnings, tents, truck tarpaulins, sails etc. are directly exposed to sunlight and thus represent ideal surfaces for energy generation, November 2008 - based on earlier work of the German Textile Research Center North-West e.V. (DTNW) - the three-year EU project within the framework of FP7 DEPHOTEX (Development of Photovoltaic Textiles based on novel Fibers), in which 13 partners from 7 European nations participate in addition to the DTNW. In the research project for the development of textile-based solar cells, which combine flexibility, low weight and longevity, the photoactive layers are applied layer-by-layer to various textile substrates with the help of different materials and technologies, whereby organic solar cells are investigated in addition to dye solar cells.

The one in December 2011 According to published results, light and flexible show large-area single cells of up to 6 cm2 a constant efficiency of about several months 2 %. A market launch should take place as soon as the efficiency on values ​​of about 3 % - 4 % increased and the long-term stability in everyday use has also been proven.

end 2008 represents Sony at the Eco-Products trade fair in Tokyo for the first time prototypes of graphically elaborate dye solar cells, which are known under the name Hana Akari to be marketed. Arranged as a cube, they are presented as lampshades that use both (when switched off) the ambient light and (switched on) their own lamp light. It should be possible to manufacture the cells in any desired color and shape, their current efficiency is 4 %. It is not announced whether and when the technology will be launched.

For other dye solar cells, Sony did in June 2008 already an efficiency of a little more than 10 % and a module efficiency of 8,2 % achieved, which through further improvements to a conversion efficiency of 10 % should be increased. In fact, it will then take two years for the company to go to a follow-up exhibition in December 2010 shows the same cell type, this time under the name Hana Mado (Blumenkraft or 'Flower Power'). This time too, without making any statements about the start of production.

Very similar, but smaller cells with an efficient order 8 % be around 2009 from the Japanese electronics company TDK presented.

In the year 2009 News circulated in April that researchers from Oregon State University and Portland State University found that Diatoms known microscopic algae could possibly triple the electrical output of dye solar cells (see below: diatom solar cells).

In November 2009 is the startup company LivinGreen Materials one of the finalists of the Cleantech Open competition. Under the name of AggraLight Here a new technology has been designed in which the surface of DSC cells is enlarged by structuring aggregates of nanoparticles so that the incident sunlight “bounces around” more within the layer in order to reduce scattering. This should double the efficiency and cut the manufacturing costs by more than half. Which is not so easy to implement, however, because until the current update in the middle 2012 LivinGreen can no longer be heard.

A report from December caused a stir 2009 from the Monash University in Melbourne, where researchers, in collaboration with experts from the Universities of Ulm and Wollongong, have found a way to significantly increase the energy yield of dye-sensitized solar cells. The scientists under the direction of Udo Bach succeed in Tandem dye solar cells manufactured in such a way that their efficiency could triple in the long term. The tandem cell consists of two stacked solar cells made of different materials that are designed for specific wavelength ranges. In order to ensure the charge transport between the layers, an efficient and transparent photocathode made of nickel oxide is being developed instead of the (non-transparent) metallic cathode that has been mostly used up to now, but this has to be further optimized. The current efficiency of around 2,4 % should be tripled by further improvements.

In June 2010 the results of an international competition are published in which the EPFL + ECAL Lab (a division of the Ecole polytechnique fédérale de Lausanne, which works together with the University of art and design Lausanne) invited students to submit their ideas for the use of dye solar cells to introduce. Of the more than 80 contributions, that would be Floating chair by Diana Chang from the California College of Arts an interesting design that is also relatively easy to implement - assuming there is no vandalism. The minimalist park bench has a transparent supporting structure covered with solar cells, which collects energy during the day in order to glow at night.

The Irish company based in Dublin SolarPrint Ltd. becomes 2008 by Dr. Mazhar Bari, Andre Fernon and Roy Horgan to develop 3rd generation dye-sensitized solar cells - which can be printed at extremely competitive costs using cheap raw materials. The essential element of the cell is the electrolyte layer, which is otherwise applied as a liquid, which often causes problems and which, in the SolarPrint process, is replaced by a printable electrolyte paste made of carbon nanotubes, graphene and ionic salts. The company expects to be able to reduce manufacturing costs to less than a quarter of the costs of conventional processes.

In July 2010 SolarPrint receives € 1.6 million investment funding from Enterprise Ireland, Custom House Capital and private investors. At the same time, the existing pilot production in Sandyford, Dublin, will be expanded and a new headquarters will be opened. The company also signs a contract with automaker Fiat to develop solar panels that can be built into the roof of the vehicles. And together with the Taiwanese Industrial Technology Research Institute (ITRI), we are working on consumer applications in which the new cells can be used. After the technologies are patented 2011