Advancing the Photovoltaic Industry

Researchers have long explored ways to incorporate quantum dots in solar cells to increase efficiency in photovoltaic technology. But success has been limited.

OPtoElectronic Nanodevices (OPEN), a client company of the NYSERDA-funded Directed Energy business incubator, believes it has fixed this problem with a new material called Q-BIC™, which stands for quantum dot with built-in charge.

OPtoElectronic Nanodevices LLC Logo Quantum dots are nanoparticles of semiconducting materials, each just a few billionths of a meter wide. At this size, the crystal particles contain vastly different optical and electrical properties than their corresponding bulk material.

Although adding quantum dots in a variety of materials has shown a substantial increase in energy harvesting, an increase in a quantum physics phenomenon called “recombination” cancels out these energy advancements. Essentially, the quantum dots absorb much of the energy created by the matrix material. This absorption translates into wasted power through heat instead of electricity.

Q-BIC is based on added “impurities” in the semiconductor-based materials that offer an additional negative charge into the quantum dots. This negative charge creates barriers that prevent the electrons from being absorbed by the quantum dot. Instead, the electrons, produced by the energy of sunlight, are repelled from the dots to be collected as electricity in the external circuit.

“We discovered that if we charged quantum dots and then we control the charge along with placing these special impurities, we are not only able to produce energy from infrared light, but we can also reduce recombination significantly,” said Vladimir Mitin, a professor in the Department of Electrical Engineering at the University at Buffalo who serves as the company’s acting CEO.

Using quantum dots with a built-in charge as the absorbing photovoltaic material offers the potential to replace traditional solar-cell materials such as silicon, which is less efficient.

One unique benefit of these quantum dots is that they can be “tuned” across a wide range of energy levels simply by changing their size. This technique reduces the need to add additional layers in multi-junction solar cells.

In multi-junction cells, a variety of materials are used, with each layer (typically three) absorbing different wave lengths, allowing energy to be harvested from different regions of the electromagnetic spectrum. This makes solar panels more efficient (up to 40 percent). But the solar panels are expensive and difficult to manufacture.

OPEN uses gallium arsenide and indium arsenide, which are conventional solar cell materials (along with other materials that serve as “impurities”) to create its Q-BIC product. But many other materials could work, according to Mitin.

The team, which has spent $3 million over the last five years to develop its product, is collaborating with the U.S. Army Research Laboratory in Maryland to further improve its material for efficient solar cells.