Towards 21% Efficiency Silicon Solar Cells with Rear Passivation in Non-Ultra Clean Facilities: the Development of a Simplified Fabrication Process Achieving 670mV/ 660mV Open-Circuit Voltages using FZ and Cz Silicon Wafers

Abstract

The development of a simple fabrication process of silicon solar cells n+p with rear passivation is presented. Each optimized step was monitored by the photoconductive decay technique. The starting materials presented thickness about 300micron and low resistivity: FZ (0.5Ohm.cm), Cz - type 1 (2.5Ohm.cm) and Cz - type 2 (3.3Ohm.cm). The Gaussian profile emitters were optimized with sheet resistance between 55Ohm/sq and 100Ohm/sq. After alneal, the maximum effective lifetimes measured at the excess carrier concentration corresponding to 1 Sun operation point at open-circuit condition were approximately 0.09ms, 0.25ms and 0.35ms for FZ, Cz-type 1 and Cz-type 2, accordingly. Excellent implied open-circuit voltages of 670.8mV, 652.5mV and 662.6mV, respectively could be associated to these measured lifetimes, representing solar cell efficiencies up to 20% if a low cost anti-reflection coating system random pyramids and SiO2 layer is considered, even if a typical industrial wafer (Cz silicon with low resistivity) is use