ICFO researchers raise organic solar cell efficiency by 0.85% by cutting re-emitted light
An experimental organic cell from ICFO emits less light at wide angles. It targets Boltzmann loss, a factor separate from the heat losses most earlier studies addressed.
Researchers at the Institut de Ciències Fotòniques (ICFO) have demonstrated an experimental approach to solar cell design that reduces the energy lost to re-emitted light, engadget.com reports. In an organic solar cell, the change improved efficiency by around 0.85 percent. engadget.com
engadget.comengadget.comOpen source ↗ The work was published in the journal Energy & Environmental Science.
Boltzmann loss instead of heat
Solar panels contain a semiconducting material, most commonly crystalline silicon, that releases electrons under sunlight and creates an electric current. Part of the absorbed energy turns into heat or is re-emitted as light.
Scientists have explored several ways to reduce thermal losses, including changing the panel's semiconductor. The light component has so far been harder to address. ICFO focused on Boltzmann loss, the energy lost to the light the cell itself emits. The authors describe the problem as a mismatch between the narrow sunlight absorption and the wider emission cones of solar cells.
What the team changed
The researchers started with an organic solar cell rather than a silicon one. They replaced the cell's indium tin oxide front electrode with a thin silver electrode and turned the cell into an optical cavity. The resulting cell still let sunlight in but emitted less light at wide angles. engadget.com
engadget.comengadget.comOpen source ↗
The gain of about 0.85 percent is modest. First author Dr. Francisco Bernal Texca said in an ICFO press release that if the emission cone can be narrowed to match the absorption cone of incoming sunlight, which the work demonstrates experimentally, solar cells will in principle be able to approach efficiencies close to 43 percent. According to the report, the underlying principle should apply to all kinds of photovoltaic cells, not only the materials used in the laboratory.
For comparison, the Shockley-Queisser limit is 33.16 percent, while consumer solar panels typically perform at 20 to 23 percent. In July, the Chinese company LONGi unveiled a solar cell with 35.5 percent efficiency and claimed that the photovoltaic cell it uses is also theoretically capable of reaching 43 percent.
