Open-circuit voltages: Theoretical and experimental optimizations of rear passivated silicon solar cells using Fz and Cz wafers

The theoretical and experimental open-circuit voltage optimizations of a simple fabrication process of silicon solar cells n+p with rear passivation are presented. The theoretical results were obtained by using an in-house developed program, including the light trapping effect and metal-grid optimization. On the other hand, the experimental steps were monitored by the photoconductive decay technique. The starting materials presented thickness of about 300 μm and resistivities: FZ (0.5 Ω cm), Cz-type 1 (2.5 Ω cm) and Cz-type 2 (3.3 Ω cm). The Gaussian profile emitters were optimized with sheet resistance between 55 Ω/sq and 100 Ω/sq, and approximately 2.0 μm thickness in accordance to the theoretical results. Excellent implied open-circuit voltages of 670.8 mV, 652.5 mV and 662.6 mV, for FZ, Cz-type 1 and Cz-type 2 silicon wafers, respectively, could be associated to the measured lifetimes that represents solar cell efficiency up to 20% if a low cost anti-reflection coating system, composed by random pyramids and SiO2 layer, is considered even for typical Cz silicon.