New nanoparticle will lead to increased efficiency of infrared lasers and solar cells

While last winter’s long period of frigid weather left many Torontonians wishing for the sun, researchers in the Edward S. Rogers Sr. Department of Electrical & Computer Engineering (ECE) were working to capture its energy more efficiently. ECE researchers recently created and tested a new type of nanoparticle that illuminates an exciting future for quantum photovoltaics.

The discovery makes use of colloidal quantum dots (CQD), which promise to be useful in high-efficiency solar technology. Also known as “artificial atoms,” the tiny, semiconducting crystals are sufficiently small to be governed by the laws of quantum mechanics. Led by Professor Ted Sargent and post-doctoral fellow Zhijun Ning, researchers have discovered a new method of creating high-efficiency CQD solar cells.

The study, which was published in Nature Materials, was carried out in collaboration with King Abdullah University of Science and Technology, Huazhong University of Science and Technology, and Dalhousie University.

In 2012, the Sargent Group created a CQD photovoltaic device that reached an efficiency of seven per cent. Now, the air-stable nanoparticles created by the Sargent Group boast an efficiency of eight per cent.

“The field of [CQD] photovoltaics requires continued improvement in absolute performance, or power conversion efficiency,” said Sargent. He added, “The field has moved fast, and keeps moving fast, but we need to work toward bringing performance to commercially compelling levels.”

Although the cells’ eight per cent efficiency is lower than that of traditional photovoltaics, quick progress is possible thanks to a quantum mechanical property known as multiple exciton generation — a single photon can cause more than one electron to jump across the band gap of a solar cell.

“Our work is motivated by the desire to produce energy-capture sources that take advantage of the free, clean resource that is solar energy,” Ning said, “Firstly, quantum dots are good at light harvesting in infrared region, which is important to increase the overall efficiency of solar cells. Additionally, they are manufacturable using liquid solutions, which can reduce the cost, and enable flexible, paintable, wearable solar cells.”

Ning also explained that the strong bonding of iodide on the quantum dots’ surface would lead to the improved performance of LEDs constructed with quantum dots. Similarly, quantum dot-based infrared lasers, which could have numerous applications in communications and computing, will enjoy increased efficiency thanks to this discovery.

The researchers anticipate that atmospheric gases such as nitrous oxide could be monitored with these materials after further research.

Correction (August 1, 2014): A previous version of this article indicated the nanoparticle was created using photovoltaics. This is incorrect. The nanoparticle was created for use in photovoltaics. The Varsity regrets the error.

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