I resent the noise of the printer, printer jams, shaking the toner cartridge, the harsh chemicals involved, and the amount of electricity it takes to print on a sheet of paper. I resent those things with the heat of a thousand suns.

But … just when I believed that I had calcified in my negative stance on all forms of printing, I learned that MIT engineers recently revealed a process they’ve developed to produce printed solar cells.  Their flexible cells can be printed on paper or fabric and folded over 1,000 times without losing efficiency, and they’re not energy-intensive to produce!  I was cautiously optimistic: maybe, I thought, printing doesn’t have to be completely evil?

Photos: Patrick Gillooly/MIT

The creation of typical solar cells involves exposing substrates to intense chemicals and high temperatures, which necessitates a whole lotta energy consumption.  MIT’s new fancy solar cells “are formed by placing five layers of material onto  a single sheet of  paper in successive passes. A mask is utilized to form the cell patterns, and  the entire printing process is done in a vacuum chamber” (Singh).  Fabric and paper substrates weigh less than the glass and other heavy backing materials that are typically used, and researchers think that they’re well on the way to developing scalable cells for use in photovoltaic arrays.

So here’s what I’ll say: the day my office printer can power itself by printing out solar cells is the day I will let go of these negative emotions and learn to forgive.

Click  here to see the technology in action (via Inhabitat).

WU XING:

I have filed MIT’s solar cells under water (because of the gentle process) and wood (because they’re flexible and can be printed on paper). And also, privately, under awesome.

Cited:

Singh, Timon. “MIT Unveils Flexible Solar Cells Printed on Paper.” Inhabitat.com 07/11/11. Accessed 07/12/11. URL.

Scientists have been working with carbon nanotubes (essentially, rolled up sheets of graphene) to encourage solar cells to convert more of the sun’s energy to electricity.  Theoretically, nanotubes “gather more electrons that are kicked up from the surface of a PV cell, allowing a greater number of electrons to produce a current” (Boyle).  More electrons means more power, so it’s a decent line of research to pursue.

image courtesy roselawgroup.com

In practice, however, using carbon nanotubes in solar cells has proved more complicated than one might like for two reasons: “first, the making of carbon nanotubes generally produces a mix of two types, some of which act as semiconductors (sometimes allowing an electric current to flow, sometimes not) or metals (which act like wires, allowing current to flow easily). The new research, for the first time, showed that the effects of these two types tend to be different, because the semiconducting nanotubes can enhance the performance of solar cells, but the metallic ones have the opposite effect. Second, nanotubes tend to clump together, which reduces their effectiveness” (Chandler). Understanding the differences between the two types of nanotubes could be useful for designing more efficient nanoscale batteries, piezoelectrics or other power-related materials.

Image credit Matt Klug, Biomolecular Materials Group

Graduate students Xiangnan Dang and Hyunjung Yi, MIT professor Angela Belcher and colleagues turned to biology for a solution to these nanochallenges, employing a genetically engineered version of a virus called M13, prone to attacking and infecting bacteria.  M13 can arrange and order nanotubes on a surface.  The virus has peptides that bind to the nanotubes, allowing them to separate the tubes so they can’t short out the circuits, and it also prevents clumping. “Each virus can grip about five to 10 nanotubes each, using roughly 300 of the protein molecules. The viruses were also genetically engineered to produce a layer of titanium dioxide, which happens to be the key ingredient in Grätzel cells, a.k.a. dye-sensitized solar cells… This close contact between TiO2 nanoparticles helps transport the electrons more efficiently” (Boyle).

Interestingly, the viruses also make the nanotubes water-soluble, which could lower manufacturing costs by facilitating the incorporation of nanotubes into solar cells at room temperature.  The virus-built structures enhanced the solar cells’ power conversion efficiency to 10.6 percent from 8 percent. That’s about a one-third improvement, using a viral system that makes up just 0.1 percent of the cells’ weight (Boyle). A little help from biology goes a long way.

WU XING:

I have filed this under fire, because the main idea relates to energy.

Cited:

Boyle, Rebecca. “MIT Researchers use Viruses to Build More Efficient Solar Panels.” Popsci.com 04/25/11. Accessed 04/26/11. URL.

Chandler, David L. “Solar Power Goes Viral.” MIT News Office. 04/25/11. Accessed 04/26/11. URL.