Metal contact recombination in monoPoly™ solar cells with screen-printed & fire-through contacts

Abstract

We present a detailed analysis of the contact properties with screen printed fire-through (FT) metal pastes on phosphorus doped (n+) polysilicon (poly-Si) layers. Two different pastes are evaluated for their contact resistivity and contact recombination on n+ doped poly-Si and on n+ doped c-Si. We present excellent contact resistivity (ρc) values ~ 1.5 mΩ-cm2 measured by the transfer length method (TLM) for metal contacts with doped poly-Si layer. The recombination at the metallized contacts is evaluated by analyzing the photoluminescence of the samples together with the Griddler software. In this work, we report ultra-low saturation current density values of 35 fA/cm2 under the metal contacts. We demonstrate that solar cells with a rear passivated contact show an average + 16 mV improvement in cell open circuit voltage as compared to the standard cells when using well-suited rear metal pastes. Efficiency of 21.8% is reported for cells printed with the best performing paste on large-area (244.3 cm2) commercially available n-type Czochralski grown Si wafers.