When it comes to producing nanoparticle-sized semiconductors called quantum dots, scientists are now looking to earthworms to do their dirty work.
Like all semiconductors, the conductive properties of quantum dots are very specific to their crystals’ size and shape. But quantum dots have an advantage because scientists can precisely control the size of the crystals formed, and the resulting conductive properties of the dots. Their applications include LED lights, solar cells, and tiny lasers. Since quantum dots absorb and emit light, they may also aid in medical imaging, but thus far scientists have struggled to incorporate these dots into living cells. Because they are potentially toxic, the dots must undergo a number of chemical reactions before they are able to enter or attach to living cells. Scientists now think the trick to making the dots compatible may lie in producing the dots within living organisms.
The quantum dot has many super powers. It can capture light energy for solar panels, team up with LEDs to emit entangled photons, and according to new research, activate neurons in a Petri dish. Quantum dots are tiny bits of semiconductor material, and their unique properties coming from being so small—no more than 10 nanometers across—that they’re governed by weird rules of the quantum world. Quantum dots are already used in biology to label individual cells or proteins. But now, quantum dots are no longer just labels; they can change how neurons behave.
A new type of solar cell using “quantum dots” may double the theoretical efficiency of current solar cells–allowing a panel to convert around 60 percent of the sun’s energy that it laps up into electricity. The research on these new cells appeared Friday in Science.
Current silicon-based solar cells lose about 80 percent of the sun’s energy they take in. It’s an inherent flaw: even working at their theoretical ideal, these cells would still lose 70 percent.
We can blame the sun’s diversely energized photons for this inefficiency. Silicon cells can only purposefully harvest photons with just the right amount energy. When they strike the cell, photons with just enough juice will prod an electron into motion (and create an electric current). An overly energized photon will excite the electrons to no purpose; the electrons will just quickly give off that photon’s energy as heat.
In two steps, this project, funded in part by the Department of Energy, salvages these “hot electrons.”
“There are a few steps needed to create what I call this ‘ultimate solar cell,’” says [Xiaoyang] Zhu, professor of chemistry and director of the Center for Materials Chemistry. “First, the cooling rate of hot electrons needs to be slowed down. Second, we need to be able to grab those hot electrons and use them quickly before they lose all of their energy.” [University of Texas at Austin]