New Technology Aims to Make Photovoltaic Cells 70% More Efficient

The study was conducted at the Excitonics Lab, headed by Professor Carmel Rotschild, in the Technion Faculty of Mechanical Engineering, with assistance from the Grand Technion Energy Program and the Russell Berrie Nanotechnology Institute at the Technion, and as part of the lab’s European Research Council (ERC) RC project on new thermodynamic tools for solar cells.

Photovoltaic cells optimally utilize a very narrow range of the solar spectrum - the broad light supplied by the sun. Radiation not within this narrow range merely warms these cells, and is not utilized. This energy loss limits the maximum efficiency of current solar cells to around 30%.

In a paper recently published in Nature Communications, the Technion researchers describe how their technology is based on an intermediate process that occurs between sunlight and the photovoltaic cell. The photoluminescence material they created absorbs the radiation from the sun, and converts the heat and light from the sun into an “ideal” radiation, which illuminates the photovoltaic cell and enables higher conversion efficiency. As a result, the device’s efficiency is increased from 30% to 50%.

The inspiration for the technology comes from optical refrigeration, where the absorbed light is re-emitted at higher energy, thereby cooling the emitter. The Technion technology works similarly, but with sunlight.

“Solar radiation, on its way to the photovoltaic cells, hits a dedicated material that we developed for this purpose, and the material is heated by the unused part of the spectrum,” says graduate student Assaf Manor, who led the study as part of his PhD work. “In addition, the solar radiation in the optimal spectrum is absorbed and re-emitted at a blue-shifted spectrum. This radiation is then harvested by the solar cell, and both the heat and the light are converted to electricity.”

The group hopes to demonstrate a full operating device with record efficiency within 5 years. If successful, they believe it could become a disruptive technology in solar energy.

The team's report is part of The Leona M. and Harry B. Helmsley Charitable Trust reports on the Alternative Energy series of the Technion and the Weizmann Institute of Science.The Technion-Israel Institute of Technology is a major source of the innovation and brainpower that drives the Israeli economy, and a key to Israel’s renown as the world’s “Start-Up Nation.” Its three Nobel Prize winners exemplify academic excellence. Technion people, ideas and inventions make immeasurable contributions to the world including life-saving medicine, sustainable energy, computer science, water conservation and nanotechnology. The Joan and Irwin Jacobs Technion-Cornell Institute is a vital component of Cornell Tech, and a model for graduate applied science education that is expected to transform New York City’s economy. American Technion Society (ATS) donors provide critical support for the Technion—more than $2 billion since its inception in 1940. Based in New York City, the ATS and its network of supporters across the U.S. provide funds for scholarships, fellowships, faculty recruitment and chairs, research, buildings, laboratories, classrooms and dormitories, and more.