Energy conversion efficiencies over 47% have been recently achieved using conventional III–V semiconductor compounds as photovoltaic materials in tandem cells. The revision of InN bandgap to a much narrower value has extended the fundamental bandgap of the group III-nitride alloy system over almost the entire spectral region (from 0.64 eV for InN to 3.4 eV for GaN or 6.2 eV for AlN), raising the possibility of a variety of new applications. The tunable bandgap, predicted high radiation resistance, and strong absorption coefficient of the InxGa1−xN material system are promising for high-efficiency photovoltaic tandem systems. During the past few years, the interest in InxGa1−xN solar cells has been remarkable. The development of high-performance solar cells using InxGa1−xN materials is one of the most important goals when compared with the existing solar cells using Si and other III–V materials. Significant efforts and progress have been made toward this goal, while great opportunities and grand challengies exist. Most of the today’s research and progress in III-nitride have been made on the heterojunction structure, e.g., p-GaN/InGaN/n-GaN structure, where an InGaN as an absorption layer or InGaN/(Al)GaN superlattice (SL) structure is sandwitched by p- and n-GaN layers. However, despite challenging results, the use of InGaN-on-GaN as a veritable photovoltaic material is still at early stages mainly due to the severe deterioration of material quality with high-In incorporation (phase segregation and highly compressive strain) necessary to achive the desired low bandgap cell in multijunction tandem cells. Our approach comes to alleviate this annoying bottleneck in development of InGaN/GaN solar cell technology by proposing an innovative InGaN/BGaN superlattice capable to be grown lattice compatible to GaN, yet allowing the desired bandgap shrinking by dual incorporation of In and B. This opens the door for a completely lattice matched InGaN-based tandem on GaN templates.