Development of TOPCon tunnel-IBC solar cells with screen-printed fire-through contacts by laser patterning

Abstract

Interdigitated back contact (IBC) solar cells featuring passivated contacts are promising candidates to achieve record-efficiency single-junction silicon-based solar cells. However, they usually require processes that are not amenable for industrial mass production and involve great process complexity associated with patterning and alignment. In this work, we present a novel TOPCon tunnel-IBC solar cell architecture, minimizing the complexity of patterning and alignment. By adopting a local poly-Si(n+)/poly-Si(p+)/SiOx tunnel junction, this cell architecture only requires full-area deposition of various thin-film layers and is compatible with conventional fire-through screen printing. The cell architecture is realized by sequential laser patterning steps and hence no shadow masks are needed. As a critical building block, we develop a working poly-Si(n+)/(SiOx)/poly-Si(p+)/SiOx tunnel junction with implied open-circuit voltage of 727 mV and a tunnel resistivity of 0.52 Ω cm2. We also establish the required laser patterning and damage-removal processes. Finally, we demonstrate that both the electron-selective and hole-selective regions can be contacted by conventional high-temperature fire-through screen printing, hence being compatible with industrial solar cell processing. Using realistic input parameters measured on test samples, we demonstrate by computer simulation that the proposed TOPCon tunnel-IBC cells favour IBC geometry with small pitches up to the technological limit. Corresponding full device integration is currently ongoing.