High quantum efficiency InGaN/GaN solar cells with 2.95 eV band gap

We report on III-nitride photovoltaic cells with external quantum efficiency as high as 63%. InxGa1-xN/GaN p-i-n double heterojunction solar cells are grown by metal-organic chemical vapor deposition on (0001) sapphire substrates with x(In)=12%. A reciprocal space map of the epitaxial structure showed that the InGaN was coherently strained to the GaN buffer. The solar cells have a fill factor of 75%, short circuit current density of 4.2 mA/cm(2), and open circuit voltage of 1.81 V under concentrated AM0 illumination. It was observed that the external quantum efficiency can be improved by optimizing the top contact grid. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.2988894]