Solar Cells Printed on Paper

MIT researchers print solar cell on paper

Vladimir Bulovic, director of the Eni-MIT Solar Frontiers Research Center, holds a solar cell printed onto a piece of paper to spell MIT. This is the first paper solar cell, according to MIT and Eni.

Quantum dots

The paper solar cells are one of many avenues being pursued around nanoscale materials at the Eni-MIT Solar Frontiers Center. Layers of these materials could essentially be sprayed using different manufacturing techniques to make a thin-film solar cell on a plastic, paper, or metal foils. 

MIT is focusing much of its effort on quantum dots, or tiny crystals that are only a few nanometers in size. A human hair is about 50,000 to 100,000 nanometers thick.

By using different materials and sizes, researchers can fine-tune the colors of light that quantum dots can absorb, a way of isolating good candidates for quantum dot solar cells.

Nanoscale layers promise to boost solar cell efficiency

MIT experts are developing novel solar cells that call for multiple layers of nanoscale materials tuned to capture specific wavelengths, or colors, of light. One way they achieve such tuning is by using quantum dots, tiny chunks of material whose absorption color changes with particle size. To prepare the samples shown above, the researchers chemically synthesized colloidal suspensions of quantum dots in inert solvents. By carefully selecting and controlling the quantum-dot size, they produced samples with markedly different colors.

Depositing the nano layers

Using their novel printing methods, the researchers have created stacked nanostructured PVs. They can layer the nanomaterials on flexible substrates such as rollable plastic or metal foils, or they can deposit them on conventional silicon-based PVs to form “tandem” structures with boosted efficiency. Because of the crystalline nature of silicon, meshing it with other crystalline semiconductors is not easy. Nanomaterials, on the other hand, work fine because they are created in an optically active form before being deposited on the silicon. As a result, the researchers can use simple room-temperature processes, such as printing of nanostructured inks, stamping, or silk screening.

Conversion targets

According to Bulović, first-principles calculations suggest that if they do everything exactly right using a single nanostructured layer on top of silicon, they should achieve 15 percent efficient conversion—somewhat better than today’s commercial PVs. But if they combine multiple layers that are good at absorbing differing parts of the spectrum, theory says that they should get up to 25 percent power conversion.

Laboratory of Organic Optics and Electronics is forging the future of Solar Cell Technology and Quantum Dot Lighting using nanotechnology and quantum chemistry expertise

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