||The efficiency of Si-solar cells has its limitation due to the intrinsic properties of Si, such as indirect bandgap with low absorption coefficient and a bandgap of 1.1 eV, which cause missing the lower energy portion of the solar spectrum and a lower efficiency for higher energy portion also. In contrast, the InGaN-based solar cells attract extensive attention nowadays mainly because they have direct bandgaps which can be tuned from 0.65 eV to 3.4 eV by varying the indium composition. InGaN solar cells have a wide range of absorption spectrum and a good potential for high efficiency solar cell with high absorption coefficient.|
For the consideration of solar cells efficiency, there is about 20 to 40 percent power loss due to the reflection from the surface and therefore, reducing the reflection from the surface of InGaN solar cells is very important in enhancing the device efficiency. In this work, subwavelength structures (SWS) on top of the device structure are investigated. Nanosphere lithographic technique is employed to create the SWSs to reduce the reflection experimentally. Also, computer model simulations are performed to optimize the SWS and analyze the device performance.
With the reflectance spectrum obtained, a modified AM1.5G solar spectrum is created as the input of the next steps to calculate the various performance characteristics of a solar cell structure. Simulation software is run to yield the current density vs. voltage curve and to analyze the efficiency improvement with the SWS AR coating. Best SWS AR structures for InGaN-based solar cells are discussed. From the study, we find that GaN SWS is best AR structure for InGaN solar cells.