InGaN Solar Cells: Present State of the Art and Important Challenges

Solar cells are a promising renewable and carbon-free electric energy resource to address the fossil-fuel shortage and global warming. Energy conversion efficiencies over 40% have been recently achieved using conventional III-V semiconductor compounds as photovoltaic materials. The revision of InN bandgap to a much narrower value has extended the fundamental bandgap of the group III-nitride alloy system over a wider 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-x N material system are promising for high-efficiency photovoltaic systems. During the past few years, the interest in InxGa1-x N solar cells has been remarkable. The development of high-performance solar cells using InxGa1-x N 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 challenges coexist. In this paper, we present a review on the present state of the art of InxGa1-x N-based solar cells. The most important challenges toward the high-efficiency InxGa1-x N-based solar cells are discussed in the context of the recent results.