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A Clearer Outlook for Quantum Dot-Enabled Solar Windows

Researchers overcome some of the final issues with solar windows, opening the way to commercial roll out

2 min read
A young woman looks out of a large office window towards a group of neoclassical buildings. The scene is tinted yellow by light from a sun low above the horizon.
Photo: Ezra Bailey/Getty Images

Quantum dots have been knocking on the door of photovoltaics for a while now. But it turns out that maybe they should have been tapping on the window instead.

In joint research between the Department of Energy’s Los Alamos National Laboratory (LANL) and the University of Milan-Bicocca (UNIMIB) in Italy, researchers have spent the last 16 months perfecting a technique that makes it possible to embed quantum dots into windows so that the window itself becomes a solar panel.

In research published in the journal Nature Nanotechnology, the international team were able to improve upon their previous iteration of the technology by making the quantum dots from non-toxic materials while having the window be largely tint free and transparent.

“In these devices, a fraction of light transmitted through the window is absorbed by nanosized particles (semiconductor quantum dots) dispersed in a glass window, re-emitted at [an] infrared wavelength invisible to the human eye, and wave-guided to a solar cell at the edge of the window,” said Victor Klimov, lead researcher on the project at LANL, in a press release. 

Of course, this is not the first time someone thought that it would be a good idea to make windows into solar collectors. But this latest iteration marks a significant development in the evolution of the technology. Previous technologies used organic emitters that limited the size of the concentrators to just a few centimeters.

The energy conversion efficiency the researchers were able to acheive with the solar windows was around 3.2 percent, which stands up pretty well when compared with state-of-the-art quantum dot-based solar cells that have reached 9 percent conversion efficiency.

The US-Italy team’s first breakthrough last year was to make large-area solar concentrators that were free from reabsorption losses that had plagued previous attempts. This lastest breakthrough was in finding a way to toss out the cadmium quantum dots for a more environmentally friendly compound.

“Our new devices use quantum dots of a complex composition which includes copper (Cu), indium (In), selenium (Se) and sulfur (S),” said Klimov in the release: “these particles do not contain any toxic metals that are typically present” in similar systems, he added. And Klimov claims that because their quantum dots absorb light from throughout the spectrum of incoming sunlight, it doesn’t distort colors.  

The researchers acknowledge that we won’t see solar windows for sale in the near term, as bringing down production costs still remains an issue. But they believe this latest development should bring solar windows closer to the market, as their new quantum dots are cheaper than traditional dots.

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The First Million-Transistor Chip: the Engineers’ Story

Intel’s i860 RISC chip was a graphics powerhouse

21 min read
Twenty people crowd into a cubicle, the man in the center seated holding a silicon wafer full of chips

Intel's million-transistor chip development team

In San Francisco on Feb. 27, 1989, Intel Corp., Santa Clara, Calif., startled the world of high technology by presenting the first ever 1-million-transistor microprocessor, which was also the company’s first such chip to use a reduced instruction set.

The number of transistors alone marks a huge leap upward: Intel’s previous microprocessor, the 80386, has only 275,000 of them. But this long-deferred move into the booming market in reduced-instruction-set computing (RISC) was more of a shock, in part because it broke with Intel’s tradition of compatibility with earlier processors—and not least because after three well-guarded years in development the chip came as a complete surprise. Now designated the i860, it entered development in 1986 about the same time as the 80486, the yet-to-be-introduced successor to Intel’s highly regarded 80286 and 80386. The two chips have about the same area and use the same 1-micrometer CMOS technology then under development at the company’s systems production and manufacturing plant in Hillsboro, Ore. But with the i860, then code-named the N10, the company planned a revolution.

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