Phosphorus diffused LPCVD polysilicon passivated contacts


As silicon photovoltaic technology advances, charge carrier losses at the contacted interfaces of the silicon absorber are coming to dominate power conversion efficiency. The so-called passivated contact, which provides selective charge-carrier extraction while simultaneously reducing interface recombination, is thus of significant interest for next-generation silicon solar cells. However, achieving both low recombination and low resistance to charge carrier extraction has proven challenging. Here, we present a passivated contact technology based on polysilicon deposited using low pressure chemical vapour deposition (LPCVD) over an ultra-thin silicon dioxide layer, which achieves an excellent surface passivation with implied open-circuit voltage of 735 mV, a recombination prefactor below 1 fA cm−2 and contact resistivity below 1 mΩcm2.

Key to this technology is the deposition of an ultra-thin silicon dioxide interlayer under high temperature and low pressure condition, performed in-situ within a single process with the polysilicon deposition. Additionally, the passivating contact structure maintains its electronic properties at temperatures of up to 900°C and is compatible with existing industrial processes. The presented work therefore represents a significant advancement in industrially-applicable passivated contact technology.

Reference Link
K. C. Fong, T. C. Kho, W. Liang, T. K. Chong, M. Ernst, D. Walter, M. Stocks, E. Franklin, K. McIntosh, and A. Blakers, “Phosphorus diffused LPCVD polysilicon passivated contacts with in-situ low pressure oxidation,” Solar Energy Materials and Solar Cells 186, 236–242 (2018).