Design, Growth, Fabrication and Characterization of High-Band Gap InGaN/GaN Solar Cells

One of the key requirements to achieve solar conversion efficiencies greater than 50% is a photovoltaic device with a band gap of 2.4 eV or greater. ln _x Ga _1-x N is one of a few alloys that can meet this key requirement. InGaN with indium compositions varying from 0 to 40% is grown by both metal-organic, chemical-vapor deposition (MOCVD) and molecular beam epitaxy (MBE), and studied for suitability in photovoltaic applications. Structural characterization is done using X-ray diffraction, while optical properties are measured using photoluminescence and absorption-transmission measurements. These material properties are used to design various configurations of solar cells in PC1D. Solar cells are grown and fabricated using methods derived from the III-N LED and photodetector technologies. The fabricated solar cells have open-circuit voltages around 2.4 V and internal quantum efficiencies as high as 60%. Major loss mechanisms in these devices are identified and methods to further improve efficiencies are discussed