Solar Photovoltaic Cells based on Silicon Membranes with Periodic Holes

Problem: Poor infrared absorption of crystalline silicon Technology: Theoretical investigations reveal that optical coupling becomes better as the fill fraction decreases in both nanohole and nanorod arrays as a result of the smaller optical density. In all cases, the nanohole arrays show better light coupling than nanorod arrays or homogenous silicon film. The optimal fill fraction for a finite nanohole structure is close to 0.5. A nanohole array even without an AR coating yields a higher efficiency than the AR coated homogenous film under a wide range of incident angles of sunlight. In a well-established fabrication technique, highly ordered holes can be produced on a crystalline Si wafer by lithography and subsequent etching acid. Christopher Noble crn@mit.edu