German Physicists Claim Breakthrough in Silicon Solar Cell Efficiency

Adding a layer of an organic semiconductor boosts efficiency, say scientists

March 1, 2024


Physicists at the University of Paderborn in Germany, through complex virtual simulations, have discovered that adding a thin layer of an organic semiconductor called tetracene to a silicon solar cell can achieve significantly higher efficiency. The results have been published in the journal Physical Review Letters.

Tetracene absorbs short-wave high-energy radiation, a part of which is wasted away as heat, and converts it into lower-energy forms that can be efficiently used by the silicon in the solar cell.

“Short-wave light is absorbed in this layer and converted into high-energy electronic excitations, so-called excitons. These excitons decay in the tetracene into two low-energy excitations. If these excitations can be successfully transferred to the silicon solar cell, they can be efficiently converted into electricity and increase the overall yield of usable energy,” said Wolf Gero Schmidt, a physicist at the university.

The findings were unusual because “defects” at the junction between the tetracene and silicon layers were previously thought to cause energy loss but instead act like a “lift” to move energy efficiently.

“Such ‘defects’ in solar cells are actually associated with energy losses. In the case of the silicon tetracene interface, the defects are essential for the rapid energy transfer,” explained Schmidt.

Efficiencies achieved in laboratories often have a difficult time transferring to commercial modules, as it involves questions about scalability, durability, and cost-effectiveness for large-scale production.

In the ongoing race to develop silicon solar cells that are more efficient than current solar cells on the market, scientists are increasingly using computer simulations to come up with new materials, fabrication techniques, and designs that convert more of the sun’s energy into electricity.

Recently, scientists at the U.S. National Renewable Energy Laboratory developed a new manufacturing process using computer simulations to improve electric vehicle batteries by punching tiny holes into the cathode.

Last year, a team of researchers claimed to have achieved a record efficiency of 29.9% for a semi-transparent perovskite cell. The research states how efficient thin-film tandems possess a huge potential for applications in building-integrated photovoltaics, transportation (such as vehicles and drones), and agrivoltaics, where efficiency, lightweight, and flexibility are important metrics.

Germany-based Fraunhofer Institute for Solar Energy Systems obtained a conversion efficiency rate of 26% for both-sided-contacted silicon solar cells in 2021, which is preferred across industrial production owing to their lower complexity.