That is well over the stable efficiencies of single junction thin film silicon solar cells which are around 6%.
In the red and infrared wavelength range 2 μm of silicon are not enough to absorb all light and therefore 'light trapping' is needed.
Due to its lower refractive index of around 2 comparing to the surrounding silicon (4) light is reflected back into the top cell.
This artificial word was first mentioned in a scientific publication of the University of Neuchâtel research group of Prof. Arvind Shah by the author J. Meier in the year 1995,[1] but is based on long pioneering research of several authors and of several years.
For a detailed list of publications, see the two main research group's publications website under http://pvlab.epfl.ch and under https://web.archive.org/web/20110222142422/http://www.fz-juelich.de/ief/ief-5/publicger/ Years later, other European, Japanese and American research groups started research activities in the field of improving the conversion efficiency of thin-film silicon solar cells by utilizing the stacked solar cell concept, naming the micromorph device 'hybrid' solar cell or naming the microcrystalline silicon absorber 'nanocrystalline' or even 'policrystalline' silicon.