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Organic Photovoltaics

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would come to this lecture on organic photovoltaics which is part of the king for you need you lecture series My name is legally Osmaniye senior
scientist at the department of energy conversion storage and and Technical University of Denmark
I'm part of the soul group at the energy conversion and with about 35 scientists students and technicians and we're headed by Professor Frederick Cripps on main research organic solar cell
research From chemistry and to emotional manufacturing and was situated here at a small campus outside Copenhagen who occupied 2 buildings and we have a large outdoor facility for studying how organic solar cells can prove that they can be used in
energy production and this is
an outline of what I'm going to talk to you about today 1st of all tell you little about the basic principles for the rationale behind photovoltaics in general and then I'll switch to organic photovoltaics lot that is then and what our motivation for working in this field the 2 years about how the organic solar cells are made specialty sliced including more than doubled to coating and finally a of by show you some large-scale examples of organic sources and that we have made have been so 1st of all
why use of solar energy while the energy flux from the sun there is 174 Peter Watts it's not of those reaching the surface while the world energy consumption at least
in 2013 where data was 18 . 3 terrible so the
89 that the pizza what's divided by 18 . 3 tournaments is about a factor of 4 thousand 800 so there are enormous amount of solar energy compared to what we use this can
also be shown in another way here is a comparison between the different energy resources that we have available in the air illustration shows and some spheres where the volume is that corresponds to the amount of energy available in each energy resources and as you can see that the sole aim to achieve this by far 5 the largest 1 especially if you compared to some of the other renewable energy sources such as due tomorrow and you have to buy massive etc. they only cover a small part of the energy that we actually put solar power and has a much much larger potential so this is the very reason why we want to use so I had to
that 2 main types of solar energy technologies performance solar heating the way you Princeton's he got and news this oil-rich nation to heed of liquid and this can be stored on their use for it's a legion of your house or and converted into electricity and generated but what we're concerned with 2 days sort of solar photovoltaics and diary at their diary transformation of solar energy into electric power and the
most well known of these photovoltaic technology Of course based on silicon and the 1st practical cells were developed by Bell Laboratories in the United States in 1954 they had a modest efficiency and more than fairly expensive and they were 1st used in things like the satellites for instance in 1958 the banknotes and satellite that I show here and then they were eminently suited to this purpose because it's a little difficult to put a large power plant into a satellite and wireless the solar cells are comparatively lightweight and can be used for this purpose and then later it was found that the Northern it as pure silicon for sales as for say electronic mall and Michael Thomas quit so you could use the surplus or scrap silicon from that industry and then the prices fell drastically to around 10 to 20 dollars per watt in electioneering you produced in this trend of price reductions has continued on to the present day and now we have to considerably less than 1 dollar award generator that me through different types of silicon "quotation mark takes them morning crystalline solar cells which has the highest efficiency of about 18 per cent then allowed the moral all the apology of malty Chris Klein solar cells which been somewhat less the efficiency and they are used mainly for instance and appliances that we put on top of our the rule of law and to generate electricity then in the final 1 is the amorphous the silicon solar cells which I even less efficient body % and they're used to being cheap products the
folder will take effect the 1st demonstration of offer creating electricity directly from the much sunlight was discovered by Alexander at 1 corral in 1839 and the story goes that when he was young man and 19 and working in his father's laboratory was part of a very famous family of physicist was working in the laboratory with some silver chloride and had put 2 electoral giants and when relied on he discovered that and it also produces electricity so this was the 1st observation of the
sector there is also the
photoelectric effect which was discovered by our cats in 1818 7th and this is that's what happens when 1 light shines on a metal you can sometimes expelled electrons was his discovery that underlined Sunday the core of the Nobel Prize for a detailed explanation of this phenomenon in the In metals you have the electrons they have to occupy certain discrete energy levels and to In order to expel the election out of metal had to overcome a certain potential in the work function so if the potent has less energy than them the and what function then no electrons can escape the middle but if they have a surplus an entity the elections can escape it with a certain candidate images this has some
ramifications has some explanations for the soul cells that we use that the actor materials are Samarkand doctors and here the elections also confined to certain energy bands In a similar Comdata there is forbid the energy gap between the highest in the occupied valence band it's called and then the the conduction band that is empty who what happens when you shine a light on the anatomy chilliness also is that if the energy of the incoming photons high enough isn't it photoelectric effect then an electron is promoted up into the conduction band and when that happens you have an electronic adoption ban and the corresponding quarter a positive charge in the mainland's spend and now they're free to move inside the material and what happens
in a so when the light and said this is a whole cascade of events 1st we had the absorption event where an excited state is generated so-called exit tunnel this informs the electron holds peril posted negative charge pair that we saw in the various slide this pair of Johnson's condition wander around inside the material onto that they separated from each other we charge separation as it is called and then hopefully these charges will end up at external electrodes where they can be used as in circle on
him a illustrated with a silicon solar cell they and the solar cell is made up of a thick slab of material that is
don't that this and we have made In a path for the electrons to go to 1 side of the material and the holders to the other side so the electric charges at accumulate at the electoral circumstance and what is called an end direct bandgap material and this means that you not only have to all the continent energy gap between the year valence band and the conduction band there are also some of the restrictions that makes it a little harder to but for the full and for this reason you need to make silicon solar cells somewhat sick in order to absorb all the sunlight .period the main an
interesting parameter for sources insist their efficiency the photovoltaic efficiency all power conversion efficiency and this is simply an and between the maximum power that you maximum electrical power outage you can get out of the solar cell divided by the incoming power of the light that shines onto the solos and the way that we mentioned this is that we pudding and source mission unit had to contact with them the solar cell and we shine a light on it and we use a standard lamp which he enumerates the site and that is that it has a thousand watts per square meter and a spectrum that is very similar to and
we then recalled what is called a diode characteristics and I'd curve and this is the great courage shown in this diagram here when and put a certain voltage across the solar cell and then we measure the current at the same time by stepping through a number of voltages with get In curve like this where it was prices we have .period here where the voltages 0 there we get the maximum currently short circuit current and we can get out of a solar cell and also we have here a point with had occurred is 0 but we have a maximum voltage which is called the open source voltage of the in these 2 points the power output of the solar cell is 0 because the power is the current multiplied by the voltage but in between these 2 points we have a maximum power .period so if we instead plant Powell as a function of the
I wanted to Wikipedia Green :colon here and which has a maximum somewhere in between these 2 .period and from this we can find the In maximum power output of so-and-so we can then divide them by the that part of the health and get power conversion efficiency but also another measure of the deficiencies and this is called the incident photon to current efficiency or external quantum efficiency and that is simply the Rachel between the number of electrons produce divided by the number of 4 times in the light in a given wavelength interval we promise the Is it important :colon efficiency all the
wavelengths you can see here from this source so it has a distinct regions where produces electricity between something like 400 managers and 600 and 15 to so if photons head lists energy then the full
time said 600 15 images they do not the the contribution they cannot promoted victims from the conduction from the various bent to the conduction band and if the above a certain energy and we do not have sold this maturity not optional the photons so again we have no the source selection going inside this small region here in the spectrum and this also is active there some theoretical limits to the solar cell efficiencies which has been found for some time and if we look at the solar spectrum the I prodded hearing removed and then we can imagine that every photo it and that the spectrum could be converted into electrons so free some of integrated all the photos in the spectrum then we can calculate the theoretical current that we could get out of material this is that every material has this resource certain regions and where they can absorb energy so that
we can only get decide tried to illustrate in that gray area the graph here so we can only that the radical preacher service current 4 navigate the
by-election gets worse because then the photos with very high energy gets absorbed into the material of course and promote electrons but these elections have the surplus energy and they will have a huge up the material until we reach a bank actually maximum voltage that we can get out of source of depends on the band capsized the 2 this corresponds to the longest waving from that the solar cells can absorb and so that there is a maximum voltage which is smaller the larger the wavelength that the material and control of 2 who can
multiply these to the voltage maximum wanted that we can get out and the maximum current integrated current then divided by the the power from the light that we put into it we get the maximum power conversion the efficiency theoretical for any material and this is called the shocking queasily limit after the 2 guys who discovered this fall From the formulas for this and for silicon for instance it is about 30 2 percent efficiency that we can maximize and get out of silicon solar In practice this is of course somewhat world yeah we can increase the efficiency and in different ways is 1 of the ways is to build words "quotation mark tandem solar cells if we put 2 shows on top of each other and oneself for instance take out 1 part of the solar spectrum and the other cells takes out another part of the the solar spectrum we can add up and the voltages from the 2 soft sales and an improved overall efficiency of the total solar cells this of course there is more complicated to build 2 cells for morsels from television the best
saw also efficiencies are collected by the National Renewable Energy Laboratory in the United States and clotted in this diagram that I show him in the blue curves here for silicon and you can see they have improved over time and now they have reached sort of plateau around 25 per cent of the sun very best solar cells of that type the ones that you can buy for your house etc. and have less efficiency than this that acknowledges that I even better for instance solar cells made out of a material called gallium arsenide I can be significantly better and that these tandem in Wiltshire junction solar cells that are much better but also much more costly then there are some emerging technologies and 1 of these are all Kenny solar cells which I'm going to talk about it the rest of this nature this is a relatively new ,comma onto the field and it started in about year 2000 and ending efficiencies have now climbed to around 10 % a modest 10 % so there it is much less efficient than the more established technologies but the the efficiency is still for this technology he had tried to
that makes him a realistic assessments of organic solar cells and compare them to the more established sources tilted knowledge is we didn't meet analysis of the organic solar cells reports made on 2 about 2012 know about 9 thousand scientific papers and that study and in some 10 thousand 500 individual solar cells reported on Shoney's and a small red dots in these diagrams here and you can see that they're concentrated and fairly low efficiency values were below 10 per cent annually but were sold to acknowledge a sort of 4 on a straight line if you probably efficiency versus the current that you get out of
this some universal trend for all sure technologies that follow this past year there are
some alternatives to silicon solar cells and as I said we have the organic sources other thin-film technology is like the cadmium telluride or and Conway injured getting 7 6 cells sensitized solar cells and newcomer "quotation mark perovskites which on inorganic type which contains the medal wanting the reason for people investigating these technologies of course there are a number of drawbacks to silicon solar cells Will you make silicon solar cells and you have to was of high energy input the chemical energy of silicon dioxide which is until high In order to spit that an apartment and get the silicon you need high energies will also need to melts the silicon and this has melting point apart 1 thousand 410 degrees and again this takes a lot of energy finally and they have to have a fairly high purity is not as high as in trice industry but nevertheless they have to be of high purity the technology is not very scalable there single the units that you have to assemble for instance when you make more tools and which is very labor intensive Silicon management for an indirect band Camacho's so it has a absorption so this means that you have to use fairly and item of the saw sales for this allow many plenty of reasons for investigating alternatives and 1 of the reasons I think especially attractive on the organic solar cells
and so why don't we start on solar cells where they promise and several things 1st of all I think they promise a very low cost and because they are then printed them like you would print things went on and on plastic 1st as they can be made on very large areas they're flexible comparison tool to silicon or other in organic solar cells that within our time because it's a diary Band usually is so we need a thin and L'Avventura and they can be produced under ambient conditions they don't need a high temperature saw a lot of heat and the manufacturers very fast you can do little to roll manufacture which is based on the order of 10 to 100 meters per minute and they don't use any a scuffle toxic materials so I think there are plenty of reasons why we should investigate all gaining sources although the efficiency and is very low compared to the other technology so what
is it all going so well so well as the name implies it's a so-so with acting material is based on organic compounds polymers instance but it could also mean that the substrate would Britain into the encapsulation is made out of some of the other players and that unnecessary in the solar system could be in a mechanic and I'll show you a diagram of what it looks like it's they aren't stack of materials we have actor material that there absorbs the light and creates the charge carriers in the middle and then you have players on each side for instance whole transport earlier and electron transport layer and that makes the electrons and holes go to each side of the solar cell and be connected to electrodes on the top and the bottom here are some of the
extra materials that I use for walking sources and we may used to complement 1 is a parliament and such as this P 3 aged 10 and then we have and what is called and accept a molecule which has a high affinity for elections Leeds parliament is conjugated and that means that an without alternating double and a single bonds in their molecules and and that has several effects 1 is that drastically increases the absorption of the Parliament so it can sorta like that shine on the solar cells but it also makes it possible for electrons and holes to move along such a chip we makes these to compliments and ink and then we prepared mayor the activity and the true compliments of form small domains inside the material where these different processes the absorption generation of charge carriers charge separation surgery book us and detailed structure the morphologies Court of this material has is very important for how efficiently it works that Our many
different types of polymers used this is 1 of the very active areas of research for organic solar cells can come up with new polymers that absorb different regions of the spectrum
are more efficient and conducting the charge carriers working
principle of an organic soil so I tried to to show here in exploded view of the solar cells so in the middle we had the active Indiana which are composed of these 2 complements in polymer interest shown in red and the acceptance which is in black and there they have sort of faces separated into discrete and endoscopic the domains inside the that's in there so that our parents for different types of charge carriers the holders can run in the parliamentary elections can run in acceptance and then there are on the top and bottom we have the whole transporting there and we have an electron transport there and then we have finally intellectuals on the the outside and 1 of these electrodes of course has to be seen transfer for the light to enter into the shows what happens 1st is that the light incense it gets absorbed inside the parliament and we get a that and the information on a carrier pair a positive and negative charge and then they Will move around inside the parliament material onto they reach face boundary between the acceptance the polymer and they will then challenged separated and the carriers will run to their respective electrodes where they can then be used in an extensively by
New Chance separation part of this cascade of events that is perhaps 1 of the most difficult parts the the reason is that Hong excited state that is generated in outside the parliament of the cannot therefore very the long time so it cannot travel far there before it has to be charged separately so the structure of the internal structure the morphology of the active there needs to be such that there is a very short pass on to reach the phase boundaries between the parliament and electric except the simplest the way would be to have a pilot but this is also the 1 where there is the largest distances inside the material before we reach a phase boundaries so this is not a very lean efficient way of their then structure structured 2 vessel ideals cases portrayed him in the middle if we could somehow engineer this internal structure so that distance to travel before next was on the order of 10 nanometers or so and that would be the best case but this is very difficult engineering Weiss To we're simply rely instead on the silver simply kind of reaction so when we make and the Incan dried out it will face separated by itself into domains of an appropriate size and much of the research goes into an extra improving this face separation into and discrete sizes the
solar cell can be built popular there a 2 2 various geometries you guys extracting electrons at the bottom of the holes at the top or vice-versa show if the electrons are attracted Bottom and the holes of the top of the solar cells it made the geometries called the normal geometry and there will be reason for that is perhaps that this was the 1st 1 that was realized the other way around it is for the holders to be extracted at the back electrode and the electrons at the top of troubled and this is called the convergence structure and this has some ramifications for which kind of materials that you can use as electoral in the 1st case the normal geometry then you would use Back the electrode materials like aluminum which is actually a very reactive and while in the inverted structure you can use a metals like silver which is not so active show the normal geometry type cells are almost invariably this stable then the inverted sure when you design also you also want the solar cells to be stable and have a prolonged life time so you have to think about which kind of geometry rules that you want to comply with allow
show you a few examples of how you can we make organic solar cells and to maintain technologies that people use the most used was caught spin coaching and where you have a glass substrate for instance and then you go take that fast while you drop a solution off your Inc the essential activity ink on top of this and the rotating motion than that makes me Inc surface coal flats and sand in a very short
times we get an even the slab of this is used in about 95 per cent of all the research organic sources in the main emphasis on that type of solar cells is to create high-efficiency solar cells is not very true to the nation that I shall before and large-scale production on flexible substrates and very fast this you can realize instead in roads revolt production and which we the study a great deal here hearing continues here you can have sizes that vary from state square centimeters 2 main square meters you can have a place of but perhaps km long and the main emphasis on this kind of research is to realize organic solar cells as a product and perhaps also studied things like stability issues
wrote to all production volcanic solitary cells it can be done on different types of machines but it's a fairly large scale is shown on a machine like this 1 here where you have to have a complicated set of work the 4 starts at 1 end of the machine the online the station and then goes through various stations through the machine inferences we have different printing coating stations like flexible printing station here we have the slot by coaching stationed there and then we have problems to dry out the link while it Rose told the machine we have that truly screen printing stationed there and finally the fall insult and rewind the station over here so we have many different than printing and coating technologies that we can apply in such a large-scale mission
there are principally to the different techniques that you can use 1 is courting and the others printing coating is one-dimensional techniques and left by coating which produces strives for instance the knife coating will you can cover areas of forest with your material then there are many different printing technologies which are to dimension where you can make patterns of any design and this is perhaps the most D which accounted for some newspaper printing all all printing plastic bags etc. we have taken flexible printing we have Korea printing screen an inkjet printer we have
applied all these techniques in different large-scale solar cells I'm not sure if you are in the remaining part of the picture he and 1 of them is called the freed PD which is the posters postcard-sized solar cell that is buildup of and either door 16 sales In serious errors then made by these roads roll techniques that they are not you will cost the solar cells they also have low efficiency because he won here that have shown about 2 % have examples of Tuesday four-percent now and they free for several reasons and 1 of them is that we have emitted techniques which incorporates Cossette elements we have amended engine tin oxide we don't use action technologies so everything can be done in it under ambient conditions the processing of the solar are very fast there are some of the the printing of courting stepsons fastest 20 meters per minute and we can have a huge amount of solar cells for insists on 100 meter stretch we have about 2 thousand of these has more to lose if we also
call them free openly for no other reason because we felt that it would be and good for the community if if people could get to know 1 experience these solar cells so then made freely available if you have a scientific purpose will always educational purposes you can apply for full solar cells at our home pages of new W. plastic photovoltaics
Yemeni different versions of the free world opinion this is the vehicle that we use for investigating this technology so the 1st types were IT all free In made use of the common there polymer materials that are standard creates to differences but we have also made it Free opened with many new types of organic polymers I've and the boards sources we have made solar cells on top of each other the so-called tandem solar cells and nearly made it sound sources where we have replaced silver electrodes with company
the most complicated so ourselves that we have made this way is tandem solar cells and here we printed 14 India's on top of each other and so we have the different actively has and we have a different supporting players like and the electron transport layer the whole transport earlier and different combinations layers in the middle and on the outside we have protecting players and and captured in the solar cells were very complicated endeavor and to make the
solar cells in the way that we build up the new experience to do this was starting and on a small scale we have developed a medieval quota which is simply a rotating drum with fall can be put on a meter length of fallen we can investigate the different types of printing and coating technologies in a small scale it will also build a small gold to instrument which can be put in Sidon X-ray machine and we can investigate what happens the even the ink as it tries and develops this very important the micro structural morphology and we when we were satisfied that the and last of the techniques on a smaller scale we then went on To the big machine that I showed you previously
finally we have a very large scale project which is called the solar power where we investigate how the organic solar cells can be used for producing energy and into the grid and here we have an outside installations will we have 4 the panelists for very long and large pounds 100 meters long and two-and-a-half meters high and I entered the area so they are in glide and was to be this on the news and he replaced the Dow Jones sells for this
purpose these are 100 meters long
molecules that and they contain tens of thousands of cells in serious and this is done by this mentoring and pantomime the solar cells and have shown here and of course requires that you can print and 100 long stretch of wall can cells defect free and so they are in the middle of connection and this is
actually possible as I've shown here here is an example of an IDE curveball diode characteristics in the 1st such a huge march contains 20 thousand 864 individuals small solar cells that are connected in series and the 200 meter long it has an area of 14 . 6 square meters and generates 11 . 3 kilowatts then but only a current corresponding to a single sales about 40 million "quotation mark and this I think is a testament to the ability of making huge amounts of organic solar cells virtually defect free and that means can add up the voltages off many many the solar cells in this fashion also they are fairly stable as you can see in this diagram we have many thousands of Oslo the I have been working outside and that those conditions in danger planted on the deployment of
the the solar cells for the solar power is very fast much faster than for any other solar cell technology and the reason is that it and we can use the solar cells as they have produced on a roll In silicon solar cells you have to sort of assemble manually and solar cells into Latin of panels and is extremely labor-intensive and requires a long time here you can simply rolled out they had a large role 100 meter long rule solar cells in 1 go so we can install 100 meters in say 1 minute and this means that we can install and operate about 15 kilowatts and this is only using no efficiency the materials that we have available now this is much more than any other solar cell technology sector and here I can show you the little of power the this is done it is also possible to employ this technology in many other ways here we have put these and Infiniti solar cells as we call them inside troops that are inflated and then put them on water In this you could use for Of course installations than you could call for the a pond or you could perhaps even into would be in the ocean we could cover an area and generated electrical energy this week I it
we have put the solar cells In bags on the ground and you could use this for say an expedition to a remote area and when you don't have access to electrical energy otherwise this will be a very likely light weight in the way of carrying solar cells and then rolling them out and where you want to to use will be made a small helium-filled balloons and put solar cells on the surface of this to to show that you can generate an energy In that way and with this
I would like to thank you for your the attention and I have some acknowledgment that made it to the ground for the king for you and the parts of finances support from the Danish Ministry Ministry of Science and Innovation high education and finally I would like to thank the soul group do it danish in the Technical University the Department of Energy Conversion storage thank you
Bell Laboratories
Satz <Drucktechnik>
Stoff <Textilien>
Gigant <Bagger>
F 101 Voodoo
Verteiler <Metallurgie>
Discovery <Raumtransporter>
Schnecke <Maschinenbau>
Endeavour <Raumtransporter>
Bell Laboratories
Walken <Textilveredelung>
National Renewable Energy Laboratory
Band <Textilien>
Proof <Graphische Technik>
Band <Textilien>


Formale Metadaten

Titel Organic Photovoltaics
Serientitel Clean4Yield eConference
Anzahl der Teile 21
Autor Jørgensen, Mikkel
Lizenz CC-Namensnennung 3.0 Unported:
Sie dürfen das Werk bzw. den Inhalt zu jedem legalen Zweck nutzen, verändern und in unveränderter oder veränderter Form vervielfältigen, verbreiten und öffentlich zugänglich machen, sofern Sie den Namen des Autors/Rechteinhabers in der von ihm festgelegten Weise nennen.
DOI 10.5446/18210
Herausgeber Technical University of Denmark (DTU), The Department of Energy Conversion and Storage
Erscheinungsjahr 2015
Sprache Englisch
Produzent Madsen, Morten V.

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