Research Of High-efficiency InGaN Solar Cell

With the rapid development of science and technology, problems about the fossilenergy have been placed into the spotlight. The non-renewable fossil fuels can lead tothe greenhouse effect and environmental pollution. Therefore, people are eager to findnew clean renewable energy. They turned to the solar energy--a clear and inexhaustibleenergy that can be found almost everywhere. Solar cell is a device to convert solarradiation directly into electrical energy, which is considered to be one of the best waysto use solar energy. And it is also representative as a green energy.Seeking the materials of high conversion efficiency for solar cell has been thefocus of research for a long time. Recently, InGaN alloys emerge as a new solar cellmaterials system because of their tunable energy band gaps varying from0.7eV forInN to3.4eV for GaN, and their superior photovoltaic characteristics--direct energyband gap in the entire alloy range and high carrier mobility, drift velocity and radiationresistance. Based on the advantages of InGaN above, this paper investigates the InGaNsolar cells, dose research with compositionally graded layer and multiple quantum well(MQW) structure, and simulates these two solar cells.For the application of composition grading, this thesis incorporates acompositionally graded region in the heterojunction and designs a p-GaN/n-InGaNgraded layer/n-InGaN solar cell. After the comparison with the heterojunction solarcell which has no graded layer through simulation, the result indicates that an extragraded layer can improve the performance of solar cell. Simulation predict that it canget maximum conversion efficiency (26.93%) when In composition is61%. It alsopredicts that a lightly doped thin graded layer exhibits the higher efficiency.For the application of MQW, this thesis designs a p-InGaN/i-(InGaN/GaNMQWs)/n-InGaN solar cell which have MQWs in the i-region instead of the intrinsiclayer. Simulation and comparison predict that MQW can increase the short circuitcurrent and the efficiency (up to27.13%when In composition is70%), though theopen circuit voltage drops slightly. Besides, the results indicate that the thin barrierlayer, the high temperature and more quantum wells can improve the performance ofsolar cell obviously.