Supporting Image
Nov 5, 2020 0    
Printable perovskites
The future of solar energy is . . . an inkjet printer?!

To increase our use of solar energy, we need to create more efficient, stable, and cost-effective solar cells. What if we could use an inkjet printer to fabricate a solar cell?

A solar cell is nothing but a light emitting diode (LED) operating in reverse. While an LED converts electrical energy into light energy, a solar cell converts light energy into electrical energy, taking advantage of a phenomenon called the photovoltaic effect. Its discoverer Edmond Becquerel found that when some materials absorb light, an electric voltage is created within the material, even without another energy source present.

It works like this: in a semiconducting material, a photon excites negatively charged electrons into the conduction band, so named because electrons can freely move when excited there. Semiconducting materials come in two main types—n-type, which have some “extra” electrons, and p-type, which are missing some electrons. These “missing” electrons are called holes. The real magic happens where n-type and p-type semiconductors are in contact with one another, however. When sunlight is absorbed at the p-n interface (Fig. 1), its energy excites electrons enough for them to enter the conduction band. The movement of negative charges and positive charges in opposite directions produces an electric current. This is how silicon solar cells generate the electricity that powers nearly all aspects of our lives today.

The first solar cells were installed on New York City rooftops in 1884 and had only a 1-2% energy conversion rate. By the 1950s, solar cells were ready for commercial production and boasted a still-underwhelming efficiency of 6%. Since then, the main goal of solar cell research has been continuously to improve their efficiency, while also lowering the cost of the materials needed for solar cell panels. Apparently, this is not an easy task, since commercial solar cells still have a maximum efficiency of only 18-20%. Solar cells produced in the lab have achieved up to 45% efficiency, but the methods used to produce these cells are too expensive to be applied to mass production.

A new type of solar cell uses a class of materials called perovskites. Perovskites have a special crystal structure (Fig. 2), with chemical formula CsPbX3, where X is a halogen element like chlorine (Cl), bromine (Br), or iodine (I). Our team fabricates perovskite films of different thicknesses—one, two, or three layers—and analyzes their properties to decide which are the best candidates for use in solar cells.

The method we use to produce these perovskite solar cells is surprisingly simple and cheap. We start with emptied refillable printer ink cartridges and fill them with the desired perovskite solutions. The substrates on which we will deposit the perovskites are mounted on a CD, which is inserted into the printer. The printer’s original CD printing software is then used to print out a “colored” image, with the perovskite solution corresponding to each of the original ink colors printed on the substrate in place of that color (Fig. 3). Using this method, multiple perovskite films can be printed at the same time, and the films can even be reprinted for a multilayer design. This allows us a great deal of flexibility to alter the thickness, fluorescence, and other film properties that will affect its performance in a solar cell.

Once we have printed the perovskite films, we study their electric transport properties—specifically, how charge is stored (capacitance) and how charge flows (current) as we alter the voltage applied to the material. This allows us to identify the perovskite formulas with the most desirable properties for use in solar cells, and we can then work to optimize these perovskite films for energy conversion efficiency and lifespan of the solar cell.

Because of their low cost, inkjet-printed solar cells are a very promising technique to improve the availability of solar energy in the future. Learn more about the process in the video below!

Fig. 1 (Click to enlarge). The solar cell functions as a p-n junction.When sunlight is absorbed at the p-n interface, an electron-hole pair is formed, creating an electric field that forces the electrons to move towards the
Fig. 1 (Click to enlarge). The solar cell functions as a p-n junction.When sunlight is absorbed at the p-n interface, an electron-hole pair is formed, creating an electric field that forces the electrons to move towards the "n" region and the holes towards the "p" region. The electric current in the external circuit flows from positive terminal to the negative terminal and the ammeter (labeled "A") measures the current. Diagram courtesy of Victor Sabirianov.
Fig. 2 (Click to enlarge). The crystalline structure of the perovskite CsPbBr3. Diagram courtesy of Ian Evans.
Fig. 2 (Click to enlarge). The crystalline structure of the perovskite CsPbBr3. Diagram courtesy of Ian Evans.
Fig. 3 (Click to enlarge). Optical photograph of the perovskite films under ultraviolet light shows that the films are photoluminescent.
Fig. 3 (Click to enlarge). Optical photograph of the perovskite films under ultraviolet light shows that the films are photoluminescent.
TAGS: #conduction    #crystals    #Electrons    #energy    #Photons    #photovoltaics    #semiconductors    #solar cells    #solar energy    #thin films    
 
SHARE THIS POST:

Related Posts

05/19
Supporting Image
Supporting Image
Electric Crystals, Part 3

Students make paper models of crystal unit cells and build a large crystal structure together while reflecting on the role of symmetry in crystal formation. This lesson is part 3 of a 4-part student-driven, lecture-free series, in which students will do card sorts, build hands-on models, solve engineering design puzzles, and more!

0 0    
05/18
Supporting Image
Supporting Image
Electric Crystals, Part 1

Crystals aren't magic, but they are amazing! In this engaging, comic-driven lesson, students do individual and group-based activities to understand the characteristics of crystals (like quartz) versus amorphous solids (like glass). This lesson is part 1 of a 4-part student-driven, lecture-free series in which students will do card sorts, build hands-on models, solve engineering design puzzles, and more!

0 0    

More Funsize Research

04/20
Supporting Image
Supporting Image
Fluids and filling

You take a pristine-looking Oreo from a package of seemingly identical sandwich cookies, and you decide to open it up to eat the creme filling first. You gently twist the cookie apart without breaking the chocolate wafers, but the creme sticks to one side only. Why? Happily, the physics of fluids helped two MIT students solve this delicious mystery. Read on to find out what they learned, and how you can test their results at home.

0 0    
05/12
Supporting Image
Supporting Image
Laser memory

Instead of pencil, paper, and eraser, we can use combinations of lasers and magnetic materials to write, read, and and erase information by varying the temperature and magnetic field. Here we apply our laser "pencil" to magnetic "paper" to write the letter “N” (Go Huskers!!). This technique allows us write, erase, and rewrite tiny magnetic memories like those found in your computer hard drive and other devices. Click to learn how it works!

0 0    
04/20
Supporting Image
Supporting Image
Thermalizing nanowires

It’s a hot summer day. You desperately want something cold to drink, but unfortunately, your bottle of root beer has been sitting in a hot car all day. You put it into a bucket full of ice to cool it down. But it’s taking forever! How, you wonder, could you speed the process up? The same question is important for understanding how electronic devices work, and how we can make them work better by controlling the temperature of the electrons that power them. Read on to find out what a bottle of root beer in a cooler full of ice and a nanowire in a vat of liquid helium have in common!

0 0    
02/23
Supporting Image
Supporting Image
World's smallest diode

Diodes, also known as rectifiers, are a basic component of modern electronics. As we work to create smaller, more powerful and more energy-efficient electronic devices, reducing the size of diodes is a major objective. Recently, a research team from the University of Georgia developed the world's smallest diode using a single DNA molecule. This diode is so small that it cannot be seen by conventional microscopes.

0 0    
02/01
Supporting Image
Supporting Image
Liquid magnetism
by Robert Streubel, Scott Schrage

You may have heard that there are three main phases of matter: solids, liquids, and gases (plus plasma if you want to get fancy). Liquids can take virtually any shape and deform instantly. Solid materials possess interesting electronic and magnetic properties essential to our daily life. But how about designing rigid liquids with magnetic properties? Impossible? Not anymore. Click to learn more!

0 0    
12/08
Supporting Image
Supporting Image
Nanoscale fluid mechanics

We think we're pretty familiar with how ordinary liquids behave, but it turns out that some of the basic things we know are no longer true when we look at these liquids on short enough length scales and fast enough time scales. The liquids start to behave more like solids, pushing back when you push on them, and slipping across solid surfaces instead of being dragged along. Click to ride the tiny-but-mighty new wave of nanofluidics!

0 0    
11/05
Supporting Image
Supporting Image
Building a better computer
by Peter Dowben, Jocelyn Bosley

Scientists are working to develop electronic devices that store and process information by manipulating a property of electrons called spin—a research area aptly known as spintronics. The semiconductors we are developing will not only be faster and cheaper than those used in conventional devices, but will also have more functionality.

1 1    
11/05
Supporting Image
Supporting Image
Good vibrations

Materials that are absolutely perfect—in other words, materials that contain no defect of any kind—are usually not very interesting. Imagine being married to a saint: you would quickly be bored out of your mind! Defects and impurities can considerably change many properties of materials in ways that allow a wide range of applications.

0 0    
11/05
Supporting Image
Supporting Image
Secrets of semiconductors

Semiconductors are materials with properties intermediate between metals and non-conducting insulators, defined by the amount of energy needed to make an electron conductive in the material. The non-conducting electrons occupy a continuum of energy states, but two of these states (the “heavy hole” and “light hole”) are nearly identical in energy. The heavy hole is easy to observe and study, but the light hole eludes most observers.

0 0    
11/05
Supporting Image
Supporting Image
Locking up electrons

Solids are generally divided into metals, which conduct electricity, and insulators, which do not. Some oxides straddle this boundary, however: a material's structure and properties suggest it should be a metal, but it sometimes behaves as an insulator. Researchers at the University of California, Santa Barbara are digging into the mechanisms of this transformation and are aiming to harness it for use in novel electronic devices.

0 0    
11/05
Supporting Image
Supporting Image
Nanomagnetism

You may know that the media used in magnetic recording technologies, such as computer hard drives, are made of millions of tiny nanomagnets. Each nanomagnet can be switched up or down to record bits of information as ones and zeros. These media are constantly subjected to magnetic fields in order to write, read, and erase information. If you have ever placed a magnet too close to your laptop or cell phone, you know that exposure to an external magnetic field can disrupt information stored this way. Did you know that it is possible for the nanomagnets to "remember" their previous state, if carefully manipulated under specific magnetic field and temperature conditions? Using a kind of memory called topological magnetic memory, scientists have found out how to imprint memory into magnetic thin films by cooling the material under the right conditions.

0 0    
11/05
Supporting Image
Supporting Image
Slow reflection

Inside solids, the properties of photons can be altered in ways that create a kind of "artificial gravity" that affects light. Researchers at the University of Pittsburgh tracked photons with a streak camera and found that whey they enter a solid-state structure, they act just like a ball being thrown in the air: they slow down as they move up, come to a momentary stop, and fall back the other way. Studying this "slow reflection" will allow us to manipulate light's behavior, including its speed and direction, with potential applications in telecommunications and quantum computing technologies.

0 0    
11/05
Supporting Image
Supporting Image
Superfluid helium droplets

In a unique state of matter called a superfluid, tiny "tornadoes" form that may play an important role in nanotechnology, superconductivity, and other applications. Just as tornadoes are invisible air currents that become visible when they suck debris into their cores, the quantum vortices in superfluids attract atoms that make the vortices visible. Quantum vortices are so small they can only be imaged using very short-wavelength x-rays, however.

0 0    
11/05
Supporting Image
Supporting Image
Magnetic anisotropy

Would you rather have data storage that is compact or reliable? Both, of course! Digital electronic devices like hard drives rely on magnetic memory to store data, encoding information as “0”s and “1”s that correspond to the direction of the magnetic moment, or spin, of atoms in individual bits of material. For magnetic memory to work, the magnetization should not change until the data is erased or rewritten. Unfortunately, some magnetic materials that are promising for high density storage have low data stability, which can be improved by squeezing or stretching the crystal structures of magnetic memory materials, enhancing a material property called magnetic anisotropy.

0 0    
11/05
Supporting Image
Supporting Image
Detecting neutron radiation

Neutron radiation detection is an important issue for the space program, satellite communications, and national defense. But since neutrons have no electric charge, they can pass through many kinds of solid objects without stopping. This makes it difficult to build devices to detect them, so we need special materials that can absorb neutrons and leave a measurable signature when they do. Researchers at the University of Nebraska-Lincoln are studying the effects of solar neutron radiation on two types of materials on the International Space Station (ISS), using detectors made of very stable compounds that contain boron-10 and lithium-6.

0 0    
11/05
Supporting Image
Supporting Image
Printable perovskites

To increase our use of solar energy, we need to create more efficient, stable, and cost-effective solar cells. What if we could use an inkjet printer to fabricate them? A new type of solar cell uses a class of materials called perovskites, which have a special crystal structure that interacts with light in a way that produces an electric voltage. We've developed a method to produce perovskite thin films using an inket printer, which in the future could pave the way to manufacture solar cells that are surprisingly simple and cheap.

0 0    
09/30
Supporting Image
Supporting Image
Computing with fool's gold?

Fool's gold is a beautiful mineral often mistaken for gold, but recent research shows that its scientific value may be great indeed. Using a liquid similar to Gatorade, it can be turned into a magnet at the flick of a switch! Read on to learn more!

0 0    

WRITE COMMENT

Go to Top