Progress in Indium Gallium Nitride Materials for Solar Photovoltaic Energy Conversion

The world requires inexpensive, reliable, and sustainable energy sources. Solar photovoltaic (PV) technology, which converts sunlight directly into electricity, is an enormously promising solution to our energy challenges. This promise increases as the efficiencies are improved. One straightforward method of increasing PV device efficiency is to utilize multi-junction cells, each of which is responsible for absorbing a different range of wavelengths in the solar spectrum. Indium gallium nitride (In _x Ga_1−x N) has a variable band gap from 0.7 to 3.4 eV that covers nearly the whole solar spectrum. In addition, In _x Ga_1−x N can be viewed as an ideal candidate PV material for both this potential band gap engineering and microstructural engineering in nanocolumns that offer optical enhancement. It is clear that In _x Ga_1−x N is an extremely versatile potential PV material that enables several known photovoltaic device configurations and multi-junctions with theoretic efficiencies over 50 pct. This potential is driving immense scientific interest in the material system. This paper reviews the solar PV technology field and the basic properties of In _x Ga_1−x N materials and PV devices. The challenges that remain in realizing a high-efficiency In _x Ga_1−x N PV device are summarized along with paths for future work. Finally, conclusions are drawn about the potential for In _x Ga_1−x N photovoltaic technology in the future.