Several groups of HZB have been intensively researching peroxide semiconductor and silicon technology since 2015, as well as combining the two into innovative tandem solar cells. In January 2020, HZB has achieved a record of 29.15% of silicon peroxide tandem solar cells and published this work in the journal Science. Then, before Christmas 2020, Oxford Photovoltaics was able to announce a certification efficiency of 29.52%. Since then, exciting competitions to set new records have been going on. Steve Albrecht, who is engaged in peroxide thin film research at HZB's HySPRINT laboratory, explained: "The 30% efficiency is like a psychological threshold for this fascinating new technology, which may completely change the photovoltaic industry in the near future." Added Bernd Stannowski, head of the technical team. "I want to particularly emphasize the good cooperation between the different groups and research institutes of HZB. This is why we were able to develop these new tandem solar cells completely in HZB and once again achieved the world record."
The silicon peroxide tandem cell is based on two innovations. A nano-textured front side (left) and a back side with a dielectric reflector (right).
Recent research and development focuses on the optical improvement of silicon heterojunction bottom cells. Added a nano-textured front surface and a dielectric back reflector. It has now been officially confirmed by Fraunhofer ISE CalLab. The new silicon peroxide tandem solar cell has been independently certified, and its efficiency has set a world record of 29.80%.
In this new work, Dr. Philipp Tockhorn (Albrecht group) and PhD student Johannes Sutter (Becker group) studied how nanostructures at different interfaces affect the performance of tandem solar cells. Tandem solar cells consist of peroxides on silicon solar cells. Solar cell composition. First, they used computer simulations to calculate the photocurrent density of different geometries of peroxide and silicon sub-cells with and without nanostructures. Then they produced silicon peroxide tandem solar cells with different textures. Even the nano-texture on one side can improve light absorption, and can achieve higher photocurrent compared with a flat reference object. The nano-texture also slightly improves the electronic quality of tandem solar cells and makes the peroxide layer better.
The research team also improved the back of the tandem solar cell, which is designed to reflect infrared light into the silicon absorber. By using a dielectric reflector, this part of the sunlight can be used more effectively, thereby generating a higher photocurrent.
These results paved the way for further improvement. The simulation results show that the performance can be further improved by nanostructuring the absorber layers on both sides. Researchers believe that efficiencies far exceeding 30% can be achieved soon.
The game is still going on.