Bifacial n-type silicon solar cells for upconversion applications

Marc Rüdiger, Stefan Fischer, Judith Frank, Aruna Ivaturi, Bryce S. Richards, Karl W. Krämer, Martin Hermle, Jan Christoph Goldschmidt

Research output: Contribution to journalArticlepeer-review

48 Citations (Scopus)


Upconversion of sub-band-gap photons has the potential to increase the efficiency of solar cells significantly, but requires modification of the solar cells. In this paper, we present a calculation framework to assess the efficiency of a combined bifacial silicon solar cell upconverter device, which is then used to optimize the solar cell׳s front and rear side anti-reflection coatings. Our calculations show that an upconverter can increase the efficiency of an optimized solar cell by 3.0% relative. Subsequently, planar bifacial n-type silicon solar cells were fabricated with optimized anti-reflection coatings. An upconversion layer – containing the upconverter phosphor β-NaY0.8Er0.2F4 embedded in the polymer perfluorocyclobutyl – was attached to the rear side of the solar cells and an external quantum efficiency arising from the upconversion of sub-band-gap photons of 1.69% was measured under 1508 nm monochromatic excitation with an irradiance of 1091 W/m2. This corresponds to a value of 0.15 (W/cm2)−1 when normalized to the irradiance, constituting a five-fold increase compared to the previously best published normalized values that were achieved without optimized solar cells.

Original languageEnglish
Pages (from-to)57-68
Number of pages12
JournalSolar Energy Materials and Solar Cells
Early online date29 May 2014
Publication statusPublished - 30 Sep 2014


  • anti-reflection coatings
  • bifacial solar cells
  • efficiency limits
  • n-type silicon solar cells
  • upconversion


Dive into the research topics of 'Bifacial n-type silicon solar cells for upconversion applications'. Together they form a unique fingerprint.

Cite this