A cost roadmap for silicon heterojunction solar cells

Research and development of silicon heterojunction (SHJ) solar cells has seen a marked increase since the recent expiry of core patents describing SHJ technology. SHJ solar cells are expected to offer various cost benefits compared to conventional crystalline silicon solar cells. This paper analyses the production costs associated with five different SHJ cell designs, including an interdigitated back-contacted (IBC) design. Using life-cycle costing, we analyzed the current cost breakdown of these SHJ designs, and compared them to conventional diffused junction monocrystalline silicon modules. Coupling the results for current designs with literature data on technological improvements, we also present a prospective analysis of production costs for the five SHJ cells and modules. For current designs, module costs were calculated to be 0.48–0.56 USD per Watt-peak (Wp) for SHJ modules, compared to 0.50 USD/Wp for a conventional c-Si module. The efficiency bonus for SHJ modules compared to conventional c-Si modules is offset by a strong increase in metallization costs for SHJ designs, as comparatively large amounts of low-temperature silver-paste are required. For module materials, the requirement for conductive adhesives results in a small cost penalty for SHJ modules compared to c-Si modules, which is more than balanced by the effect of higher efficiency in SHJ modules. Our prospective study showed that improvements in cell processing and module design could result in a significant drop in production costs for all module types studied. The SHJ modules gain much advantage by reducing and replacing silver consumption, increased cell efficiency and thinner wafers and have prospective production costs of 0.29–0.35 USD/Wp. Conventional c-Si module cost is less sensitive to silver paste consumption, limiting the potential for cost reduction, and has prospective production costs of 0.33 USD/Wp. Replacement of indium-tin-oxide was not found to contribute substantially to a reduction in module costs.