Thin-film solar cells made of crystalline silicon are inexpensive, with efficiencies as high as about 14%, and the less light reflected from the surface, the higher the efficiency. At present, a team led by Professor Christiane Becker of Helmholtz-Zentrum (HZB) in Berlin has found a solution to this problem and applied for a patent.
"It's not enough just to bring more light into the cell," Becker said. This surface structure can damage the electronic properties of the material and ultimately reduce efficiency.
David Eisenhauer is a member of the Becker team, and his idea sounds simple: make a scattering structure with a rough surface and apply a smooth surface at the same time, so that the silicon layer can grow without defects (the most important layer of silicon solar cells) ).
The process involves several steps: first, the researchers pressed an optimized nanostructure onto a still-liquid silicon oxide precursor layer, and then bonded it with ultraviolet light and heat. The result is tiny, periodically arranged cylindrical protrusions-ideal for capturing light. However, on this rough surface, the crystalline silicon layer cannot grow perfectly, so these structures are detrimental to the quality of the solar cell. To solve this problem, researchers applied a very thin layer of titanium oxide on top of the nanostructures, making the surface smooth, so that the silicon layer can be grown without obstacles.
The professional name of the coating is smooth anti-reflective three-dimensional texture, which can reduce the reflection of light and absorb more light without damaging the electrical characteristics. The discovery has been patented.
Christiane Becker led the young research group funded by the BBMB Nano Engineering Project HZB. As part of the BerOSE Joint Laboratory, she works closely with the Zuse Institute and uses computer simulations to study the effects of nanostructures on material properties.