From sputtering to nanoprinting
Perovskite photovoltaics finally has its integrated anti-reflective layer. Thanks to a group of researchers belonging to the Fraunhofer Institute for Solar Energy ISE and the Faculty of Physics of the University of Warsaw.
The team has managed a fairly crucial feat for the segment and indispensable to achieve high conversion efficiency. The challenge was to reduce normal reflection losses by texturing the front surface of the cell. This is an easy and common process for silicon photovoltaics: in order to properly manage light, the industry affects the surface of cells with corrosive chemicals. The process creates microscopic pyramidal patterns that “trap” photons in a longer optical path. The consequence? The textured layer increases light absorption (and thus reduces reflectance), increasing overall performance.
This same approach cannot be applied to perovskite photovoltaics. The materials of this group suffer, in fact, from a marked sensitivity towards external agents. Just think of the long fight against humidity, undertaken by the segment. To improve the light absorption until yesterday we preferred anti-reflective coatings applied later by vaporization, less aggressive method but in practice even less effective.
New anti-reflective for perovskite photovoltaics
The new study conducted by the Fraunhofer ISE and the University of Warsaw has changed approach. As described in the scientific journal Advanced Materials Interfaces (English text), scientists used nanoprinting to create an efficient anti-reflective structure with honeycomb symmetry above the perovskite solar cell, without damaging it. This technique allows the production of nanoscale elements on very large surfaces, as explained by Maciej Krajewski, a researcher at the Polish university. This ensures scalability in the process.
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Tests on perovskite PV have shown that the nanoprinted anti-reflective layer reduces reflectance from 13.6% to 2.7%, which increases the current density of the cell by 2.1 mA/cm2, exceeding by 0.05 mA the result of traditional anti-reflective coatings. The method is also compatible with tandem perovskite-silicon configurations, a new milestone in solar research.