Tandem Solar Cells Just Short of 30 % Efficiency
A team from the Helmholtz-Zentrum Berlin has published a report in the journal Science on the development of its current world record of 29.15 % efficiency for a tandem solar cell made of perovskite and silicon. The tandem cell provided stable performance for 300 hours – even without encapsulation.
Solar cells consisting of two semiconductors with differing band gaps can achieve considerably higher efficiencies when used in tandem compared to the individual cells on their own. This is because tandem cells use the solar spectrum more efficiently. In particular, conventional silicon solar cells primarily convert the infrared components of light efficiently into electrical energy, while certain perovskite compounds can effectively utilize the visible components of sunlight, making this a powerful combination.
In the beginning of 2020, a team headed by Prof. Steve Albrecht at the Helmholtz-Zentrum Berlin broke the previous world record for tandem solar cells made of perovskite and silicon (28.0 %, Oxford PV), setting a new world record of 29.15 %. Compared to the highest certified and scientifically published effficiency, this is a giant step forward. The new value has been certified at Fraunhofer ISE and listed in the NREL chart. Now, the results have been published in the journal Science with a detailed explanation of the fabrication process and underlying physics. The new perovskite/silicon tandem cell is characterized by consistent performance during more than 300 hours under continuous exposure to air and simulated sunlight without being protected by encapsulation. The team utilized a complex perovskite composition with a 1.68 eV band gap and focused on optimizing the substrate interface.