Printing Perovskites

PSPINS Author

07/31/2017 Added

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Vlog describing perovskites and MRSEC PSPINS cutting edge research.

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[00:00:00.216](gentle music)
[00:00:05.336]Solar cells are a thing, obviously, super popular now.
[00:00:09.202](upbeat music)
[00:00:14.723]So, these are silicon based ones,
[00:00:16.461]but the current way of fabricating them,
[00:00:18.083]Is kind of complex and expensive.
[00:00:20.813]They typically involve things like, you heat it to hundreds
[00:00:23.912]or even thousands of degrees Celsius
[00:00:26.195]and a lot of times, you fabricate them
[00:00:27.837]in an ultra high vacuum environment
[00:00:29.021]so, it's areas that, chambers with no air
[00:00:30.849]that you suck it all out of.
[00:00:32.408]So, these are time consuming and they're expensive
[00:00:34.141]and so our hope is that we could make thin
[00:00:36.552]films out of perovskite, basically photocells.
[00:00:38.867]Cells that are not only efficient
[00:00:40.243]and turn sunlight into energy or power,
[00:00:43.219]but also to do this in a very approachable,
[00:00:45.832]cheap and flexible way. Using very basic equipment
[00:00:49.821]such as printers.
[00:00:51.048]So, this is kind of a big step, since this is an early field.
[00:00:53.651]At kind of pushing towards other forms of energy
[00:00:56.253]and maybe finding other ways of going about this.
[00:00:58.557](upbeat guitar music)
[00:01:03.624]So, we're using this molecule called a perovskite
[00:01:07.091]and they're pretty special molecules
[00:01:08.872]in that they interact with light in a special way.
[00:01:11.495]So, these materials, actually make really,
[00:01:13.821]really small crystals, they're nano size,
[00:01:16.690]and so, what happens is if you make a certain crystal
[00:01:21.009]small enough, certain properties emerge
[00:01:23.040]and they're called quantum properties.
[00:01:24.528]And so, these small crystals are called quantum dots,
[00:01:26.715]and what we care about them
[00:01:27.548]for the application of solar cells
[00:01:28.907]is that you can actually tune these quantum dots
[00:01:31.414]to accept certain ranges of energy.
[00:01:33.918]So, ultraviolet is one of the highest frequency lights
[00:01:36.900]we have, it's so high that we can't see it with our eyes.
[00:01:39.269]Higher frequency means higher energy.
[00:01:40.838]When you actually shoot these off at our materials,
[00:01:43.174]the energy is high enough to pop
[00:01:45.296]off the electrons pretty easily,
[00:01:46.614]so, we have some interesting properties that happen.
[00:01:48.353]So, if you hook it up to the proper apparatus
[00:01:50.629]you can generate a current. We know that electricity,
[00:01:52.481]or a current is basically just the movement of electrons.
[00:01:55.382]So, when it kicks out these electrons,
[00:01:57.281]it moves around through the circuit
[00:01:58.788]and then it gives us current.
[00:01:59.680]So, this is how we turn sunlight into energy or electricity.
[00:02:03.430]But they also, what happens in physics,
[00:02:05.017]is if you kick out an electron,
[00:02:06.965]sometimes it'll fall back down to where it used to be
[00:02:09.163]and a special thing happens in physics
[00:02:10.613]is when it does that, it releases sunlight as it does this.
[00:02:13.637]So, when you kick an electron up and it falls back down,
[00:02:16.080]every time an electron falls, it releases a burst of light.
[00:02:18.197]So, when we introduce high energy UV light
[00:02:20.448]to our molecules, they actually glow.
[00:02:22.378]And we talked about how quantum dots,
[00:02:24.261]and depending on the size of them,
[00:02:25.176]you can tune them to different energy ranges.
[00:02:26.957]Depending on how you tune them,
[00:02:28.035]you can actually make them emit different colors.
[00:02:30.262]So, right now, the one we mostly work with
[00:02:31.811]will glow green if you expose it to UV light.
[00:02:33.731]So, to go in further in this theme
[00:02:36.108]of low cost and approachable,
[00:02:37.709]we are using just a commercial printer,
[00:02:40.056]just one that you can buy at Walmart or Amazon,
[00:02:42.637]where instead of where a printer usually has ink cartridges,
[00:02:45.261]like red, blue, yellow, we remove those
[00:02:46.947]and instead we fill them with molecules.
[00:02:48.215]We print a picture just like you would print
[00:02:50.936]a Google doc or something,
[00:02:52.045]but instead of using black ink,
[00:02:53.304]we're using the perovskite itself,
[00:02:54.776]so we are printing, instead of printing your essay,
[00:02:57.048]we're printing a solar cell.
[00:02:59.314](upbeat guitar music)
[00:03:03.319]The origin of where I get the perovskite
[00:03:04.995]is I have to synthesize it at the lab.
[00:03:06.669]I dissolve it in hexane, so I make it into a solution.
[00:03:10.019]But basically, I refer to that as ink
[00:03:12.079]and I just simply extract it with a pipette
[00:03:14.117]and place it inside the ink cartridge.
[00:03:15.599]And you pretty much can label it as any color
[00:03:17.925]that the printer already recognizes.
[00:03:20.079]So, I basically use a software
[00:03:22.297]that came with a normal, commercial printer.
[00:03:25.061]So, you go to the software and then ask it
[00:03:26.798]to print that specific color, so, for example,
[00:03:28.803]if I placed the refillable ink cartridge
[00:03:31.311]for the color yellow, I could ask it to print yellow
[00:03:33.925]and the printer would think it's printing yellow
[00:03:35.845]but it's actually printing out the solution
[00:03:37.509]you put in the ink cartridge.
[00:03:38.629]So, it's a way of tricking the printer
[00:03:40.399]into doing what you want it to do.
[00:03:41.999]He puts a CD in and then we place the substrates on it
[00:03:45.413]and so that's something you can just load in,
[00:03:46.991]it's okay if it's a little bit thicker
[00:03:48.378]and then the printer prints on it with the molecules.
[00:03:50.969]The real benefit to this is that you could actually mix
[00:03:53.166]different solvents or solutions you know,
[00:03:55.237]while it's printing to get an array
[00:03:57.125]of different combinations.
[00:03:58.607]You know, yellow and blue makes green,
[00:03:59.898]but if you're not printing a picture,
[00:04:01.221]and you're printing a solar cell,
[00:04:02.223]you put two different molecules together,
[00:04:03.749]one for red one for yellow and then you can get,
[00:04:05.374]instead of a different color,
[00:04:06.568]you can get a different mixture of molecules
[00:04:07.566]which would give you different properties
[00:04:09.187]as a solar cell.
[00:04:10.244]So, after we print off the films and let them dry,
[00:04:12.454]we place six silver contacts
[00:04:14.289]and then I hand it over to Ben
[00:04:15.461]so he can do IV and CV testing on them.
[00:04:17.658](upbeat guitar music)
[00:04:22.300]IV is the current as a function of the voltage
[00:04:24.826]and the CV is the capacitance as a function of the voltage.
[00:04:27.889]So, that with the current as a function of the voltage,
[00:04:31.066]as the current increases, we should see the resistance
[00:04:35.800]that we're gonna get decrease.
[00:04:37.827]And then, with the IV, we want to know,
[00:04:40.794]how well it works as a capacitor
[00:04:42.810]and how well it works when it comes to the current
[00:04:45.583]and what it can handle.
[00:04:46.660]So, we look further into the photoemission spectra
[00:04:48.927]using XPS and further study,
[00:04:51.487]more electronic properties of thin films.
[00:04:54.708]Basically, it takes samples before
[00:04:56.154]and after they've been tested
[00:04:57.423]and just look at more lifetime measurements
[00:04:59.514]to add on to the efficiencies.
[00:05:01.380]We look at the measurement, electric measurements
[00:05:03.704]and we decide which ones are the best option
[00:05:06.415]for a solar cell.
[00:05:07.631](Upbeat guitar music)
[00:05:13.103]Energy is an important topic and the solar cell has got
[00:05:17.727]considerable attention in the last years.
[00:05:20.341]And our research is significant from this point of view
[00:05:23.817]because we want to improve the solar cells
[00:05:26.878]and this is the key of having cheaper solar cells
[00:05:31.017]and also to get solar cells which can be easily fabricated
[00:05:37.203]as in this case, just to print them.
[00:05:39.731]Now, that's nano.

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Printing Perovskites

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