Integration of Self-Assembled Porous Alumina and Distributed Bragg Reflector for Light Trapping in Si Photovoltaic Devices

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.