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Quantum Dots with Built-in Charge Could Lead to Highly Efficient Solar Cells

Researchers dope quantum dots to repel electrons and push energy efficiency in solar cells up around 50 percent

1 min read
Quantum Dots with Built-in Charge Could Lead to Highly Efficient Solar Cells

When you see 45 percent energy conversion efficiency for solar cells, you stop and take notice.

The story of nanotechnology in solar cells over the last decade has often been about pushing energy conversion efficiency higher and higher while dragging prices lower and lower. It hasn’t always been easy to sustain that dual-pronged attack.

Certainly, quantum dots have been looked at by researchers in this area as a possibility for achieving high conversion efficiency at a lower cost.

But I had no reason to expect that the use of quantum dots in solar cells would yield 45 percent conversion efficiency. Nonetheless that’s the figure I saw when University of Buffalo, in collaboration with both the Army Research Laboratory and the Air Force Office of Scientific Research,  announced a way of embedding charged quantum dots into solar cells that allows the cells to harvest infrared light.

The research, which was originally published in the ACS journal Nano Letters last May, used selective doping of some of the quantum dots so they have a built-in charge that repels incoming electrons. This in turn forces the electrons to travel around the quantum dots.

As the abstract explains: “We found that the quantum dots with built-in charge (Q-BIC) enhance electron intersubband quantum dot transitions, suppress fast electron capture processes, and preclude deterioration of the open circuit voltage in the n-doped structures. These factors lead to enhanced harvesting and efficient conversion of IR energy in the Q-BIC solar cells.”

The three University of Buffalo researchers behind this work—Vladimir Mitin, Andrei Sergeev and Nizami Vagidov—have spun-out a company called Optoelectronic Nanodevices LLC that presumably will attempt to commercialize this technology.

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The Transistor at 75

The past, present, and future of the modern world’s most important invention

2 min read
A photo of a birthday cake with 75 written on it.
Lisa Sheehan
LightGreen

Seventy-five years is a long time. It’s so long that most of us don’t remember a time before the transistor, and long enough for many engineers to have devoted entire careers to its use and development. In honor of this most important of technological achievements, this issue’s package of articles explores the transistor’s historical journey and potential future.

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