In this paper, we report systematic investigation of the structural and electronic properties of GaN and InxGa1-xN alloys with x up to 0.31 grown on Si (111) substrate. P-type doping of InxGa1-xN using Mg has been achieved consistently with magnesium concentrations up to 1021 atoms/cm3. The first results on photovoltaic action in InGaN p-n junctions with ∼20% In fraction grown on silicon are also reported. An open circuit voltage (Voc) of almost 1 V was measured under concentrated (20 x sun) AM1.5G condition. The diode shows the onset of a photoresponse at about 2.6 eV. Relatively low shunt and high series resistance are the key factors limiting performance of the InGaN cells with larger In content (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)