InGaN solar cells

With a direct bandgap tunable in the ultraviolet (3.42 eV) to near-infrared (0.65 eV) spectral range, InGaN is a promising semiconductor for high-efficiency photovoltaic devices to be integrated with the already existing technologies, III-V and Silicon. InGaN solar cells are currently fabricated on sapphire using metalorganic vapour phase epitaxy (MOVPE). However, their present limitations should be overcome: cost per unit of area has to be reduced using for example silicon substrates, indium incorporation should be increased to fit to the solar spectrum, and nitrogen polarity might be desirable to improve the carrier collection in In-rich nanostructured active regions. Nowadays, the plasma-assisted molecular beam epitaxy (PA-MBE) technique allows the larger In-incorporation in active layers and provides a good solution to demonstrate the proof-of-concept of all-InGaN solar cells. Last developments on the state-of-the-art of InGaN solar cells based on high-In content InGaN junctions grown by PA-MBE and InGaN/GaN multiple-quantum well structures grown by MOVPE are presented from the growth, material properties, device design and performance point of view.