While trying to increase the solar cell efficiency conversion, the photovoltaic (PV) research community seeks also the reduction of the fabrication costs (0.25-0.5 Euro/Wp) by using a low cost, large diameter substrate from a material which is abundantly available on earth, such as silicon. Indeed, a true monolithic integration of the III-V semiconductors structures with silicon is receiving great interest since it will enable simultaneous high efficiency and low cost production. The group III-nitride alloys, such as InGaN, has the unique advantage of one of the widest adjustment of direct bandgaps from 0.65 eV (InN) to  3.42 eV (GaN) range. Compared to Si, GaAs, CuInGaSe, or Ge systems, it is the only semiconductor system that provides the perfect match to the solar spectrum (0.5 to 4 eV), which opens up an interesting opportunity for high-efficiency tandem cells. Thus, lots of efforts have been devoted so far into using InGaN as an absorber in Si-based solar cells. However, despite challenging results, the use of InGaN as a veritable PV material is still at early stages mainly due to the severe deterioration of material quality with In incorporation at high concentrations necessary to acquire the desired low bandgap in a tandem cell. Our approach comes to alleviate this annoying bottleneck in development of InGaN/AlN/Si solar cells by proposing an innovative BGaN material capable to be lattice matched to AlN, yet allowing the desired bandgap shrink.