Case 09261

Ge backside solar cells to absorb un-utilized light below Si band-gap for increased energy conversion efficiency


Energy conversion efficiency, silicon solar cells, multi-junction solar cells, backside solar cells, hetero-junction, band gap energy, silicon layer


Backside coating of solar cells to improve energy efficiency


Enhancing charge collection efficiency in solar cells by increasing absorption of shorter/ longer wavelengths


This invention increases the light-current conversion efficiency of silicon solar cells by fabricating germanium solar cells on the backside of silicon solar cells. The backside solar cells absorb escaping photons below the silicon band gap, which increases efficiency by ~50% over current solar cells. The p-p junction between the silicon cell and germanium cell inactivates the detrimental effects of interface dislocations. By forming a tunnel diode using additional intrinsic layer and p++ layer, interface dislocations are not formed in the tunnel diode region.


Increases solar cell conversion efficiency by ~50% through the absorption of light below Si band gap

  • Professor Lionel Kimerling (Department of Materials Science and Engineering, MIT)
  • Kazumi Wada (Materials Processing Center, MIT)

Intellectual Property:

U.S. Patent Number 6,743,974, issued June 1, 2004



Last revised: November 8, 2010

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