A dramatic improvement in the efficiency of photovoltaic cells has been achieved

The method developed by the Technion researchers is based on an intermediate process that mediates between the sunlight and the photovoltaic cell and actually converts the solar radiation into light in an "ideal" spectrum that illuminates the solar cell and enables a higher conversion efficiency.

Researchers at the Technion have developed a technology that will significantly improve the utility of photovoltaic cells. The research, published in Nature Communications, was conducted in the Excitonics Lab under the leadership of Associate Professor Carmel Rothschild in the Faculty of Mechanical Engineering. It was held with the support of the Grand Energy Program (GTEP) and the Russell Berry Institute for Nanotechnology (RBNI) at the Technion and as part of an ERC project on behalf of the European Union of the laboratory on new thermodynamic tools for solar cells. The research was led by doctoral student Assaf Menor.

The sun is a powerful source of renewable energy. In fact, it is the only source of energy today that can satisfy the energy consumption of the human race, so it is no wonder that the use of solar energy is expanding - both in solar-thermal methods, which convert the sun's energy into electricity through an initial conversion to heat, and in photovoltaic cells (Photovoltaics) ) which convert it directly into electricity. However, various technological limitations limit the efficiency of photovoltaic cells.
According to Menor, "The photovoltaic cells know how to optimally utilize a very narrow area of ​​the broad spectrum of light provided by the sun; Radiation that is not in this narrow range heats the cells and is not used for electricity. This lost energy limits the maximum efficiency of solar cells to about 30%."

The method developed by the Technion researchers is based on an intermediate process that mediates between the sunlight and the photovoltaic cell and actually converts the solar radiation into light in an "ideal" spectrum that illuminates the solar cell and enables a higher conversion efficiency. The inspiration for this work came from optical cooling, where the absorbed light is re-emitted at a higher energy and cools the material. "Here we developed a device that does a similar thing with sunlight," says doctoral student Assaf Menor. "The sun's rays, on their way to the photovoltaic cells, hit a dedicated material that we developed for this purpose, which is heated by solar radiation that is in the unused spectral range. The radiation in the effective spectral range is absorbed, re-emitted and cools the intermediate material. The emitted radiation is harvested by the solar cell and converted into electricity. In this way, the 'lost heat' is also converted to electricity, and the result: a jump in the maximum efficiency of the device from 30%, the accepted value for photovoltaic devices, to 50%."
Manor points out that the unique material is heated by the sun's radiation to a temperature of only about 700 degrees, less than half of the temperatures typical of existing devices of this type.

Associate Prof. Carmel Rothschild is the head of the exciton laboratory and the head of the optical engineering major in the Faculty of Mechanical Engineering at the Technion, a major that combines physical optics and opto-mechanical design.
Assaf Menor is currently completing his third degree, during which he was awarded the Adams scholarship awarded to outstanding doctoral students. Menor, who completed a bachelor's degree at the Technion (electricity and physics) and a master's degree at the Solar Energy Research Center in Sde Boker, will soon leave for a post-doctorate at the University of Michigan.