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Light trapping is an important issue for thin film silicon photovoltaic cells due to the limited absorption coefficient for near infrared light. In this letter, we present a photonic structure that combines porous anodic aluminum oxide with a distributed Bragg reflector (DBR) on the backside of Si cells for light trapping. Simulation results show that this low-cost, self-assembled structure can provide more than 50% relative efficiency enhancement for a 2 μm thin film crystalline Si solar cell, as compared to a reference cell without any back structure. As a proof of concept, we incorporated the backside structure into thick silicon wafers. The enhancement of light absorption near the band edge of silicon is demonstrated for our proposed light-trapping structure, in agreement with the theoretical predictions.
Date of Publication: Sept.15, 2010