The Adaptation of Perovskite Compounds in Photovoltaics Matt Weiss | Will Humble University of Pittsburgh SSOE SOLAR NECESSITY EFFICIENCY A SUSTAINABLE FUTURE COMPOUND INTEGRATION INTO THE SOLAR PANEL PEROVSKITE COMPOUND The application of methylammonium lead iodide perovskite solar panels is a technological leap that should be capitalized on mass production for commercial use. These perovskite solar cells are made with special hybrid organic-inorganic compounds that are structured around organic molecules, like the methylammonium. They are large enough to hold a lead halide compound, like lead with iodine, in a unique structure. Electrons generated in the photovoltaic reaction with sunlight flow through the fluid electrolyte compound. The fluid electrolyte also has porous, solid methylammonium lead iodide that allows the electrons to pass through a highly efficient structured channel. The perovskite solar cells can be made in other ways like using tin instead of lead. However, the lead iodide cells have reached efficiency levels of over twenty percent compared to tin iodide cells of only six percent. Perovskite solar cells featuring methylammonium lead iodide are easy to make in a basic lab setting because the necessary materials are inexpensive to attain. Solar panels using this perovskite compound are quick, cheap, and easy to produce while still being much more efficient than the current commercial solar panels averaged at thirteen percent light conversion efficiency. Energy from solar panels produces no pollution and is not a finite resource like fossil fuels. CONTACT US Perovskite is a naturally occurring mineral: calcium titanium trioxide (CaTiO 3 ). The perovskite structure is shown in the figure below. It is modeled from CaTiO 3 and has the general form ABX 3. A and B are cations and X is the anion. The compound of interest for the perovskite solar cell is methylammonium lead iodide (CH 3 NH 3 PbI 3 ). This structure is an excellent electrolyte and efficiently separates electrons and holes due to its unique lattice shape. The perovskite compound is both strong and versatile. The figure above shows an example of how the perovskite compound is integrated into solar panels. In this example, Sunlight would go in from the bottom and continue to the top. All of the layers pictured have highly specialized functions. The first layer in an antireflective glass the protects the inner layers and optimizes the amount of light absorbed. Under the glass is a transparent conducting film, typically fluorinated tin oxide, that draws electrons in and extracts them to be used as energy. The next layer is compact TiO 2, which acts both as a hole blocking material and the n-type layer. The perovskite layer follows and it acts as a pathway for electrons. The perovskite compound has very low recombination rates. After the perovskite is the hole transport medium that acts as a heavily doped p-type layer and specializes in transporting holes. Finally, the layer of gold or silver rear contact plate acts as the cathode and replenishes the system. The current perovskite solar cells have reached light conversion efficiency levels of 19%. These solar cells are relatively new compared to the other leading types of solar cells. However, in only a short period of time, perovskite solar cells have shown large and consistent growth. Though these cells have not achieved the highest conversion rates, they are more cost effective and can be easily assembled under standard lab conditions. Solar power offers free energy that is renewable as well as ecologically friendly. Perovskite solar cells capitilize on these benefits to provide a chance for a sustainable future. Further improvements in lab tech and production efficiency have researchers predicting an economic feasibility that can compete with traditional energy resources. Some researchers are predicting as low as 10 cents per watt in the near future. Solar energy can be maintained for future generations and it has no harmful byproducts. All of these things put together make perovskite solar panels a competitive and sustainable energy resource. Harnessing the energy of the sun through the use of photovoltaics and more specifically, perovskite solar cells, may be the key to a sustainable future. The world today relies on nonrenewable forms of energy (fossil fuels) that will inevitably expire while an ever-growing world population increases energy demands. These forms of energy face a number of issues such as depleting resources, rising prices, environmental concerns, and security concerns over dependence on imports from a limited amount of countries. These issues define the energy crisis that threatens future generations, but opens a need for new form of energy to be found. The solar power field has shown great promise for providing a new source of energy. Solar power is clean, efficient, cheap, and near infinite in renewability. Harnessing the energy of the sun through the use of photovoltaics and more specifically, perovskite solar cells may be the key to solving the world’s energy crisis. ABSTRACT Solar panels utilize electron emission from the photoelectric effect. They consist of an N-type crystal, which provides electrons, and a P-type, which creates holes of charge. Both of these act as charge carriers. The figure above shows the N-type and P-type with their electrons and holes, respectively. Electrons are released from the N-type crystals and flow through the holes in the P-type crystals. This process is shown in the bottom part of the figure above. This p-n junction acts as a diode allowing electric current to flow. Though there are almost no mobile charges, the electric field pulls electrons and holes in the opposite direction. This forces electrons to flow from the P-type to the N-type. When the electrons flow back to the N-type crystalline emitter, some are picked up by the fingers and flow to the busbar. The fingers and busbar act as the top part of an electrode and are designed to receive most of the electrons while still permitting a large amount of sunlight to enter the system. Underneath the P-type layer base is the rear contact. It is meant to provide a medium for electrons to reenter and replenish the process. When the circuit is complete, the electrons’ extra energy is used as electrical power and then the electrons reenter the system through the rear contact. PHOTOVOLTAIC TECHNOLOGY