Towards industrial advanced front-junction n-type silicon solar cells

Abstract

Recent progress in the development of advanced front-junction n-type monocrystalline solar cells for potential industrial fabrication is presented. The textured, boron-diffused front surface is passivated with a stack of Atmospheric Pressure Chemical Vapor Deposited (APCVD) Al2O3 and Plasma-Enhanced Chemical Vapor Deposited (PECVD) SiNx. A champion cell with an in-house measured efficiency of 21.6% is obtained for small-area cells (i.e., 2×2 cm2) fabricated at the ANU. The high open-circuit voltage of 664 mV demonstrates the excellent passivation of both the front and rear surfaces. The cell design and process have demonstrated a good tolerance to substrate resistivity variations, with an average cell efficiencies close to 21% for resistivity varying between 3 and 10 ω·cm. Moreover, with an adaption of the process developed at the ANU, large-area cells (i.e., 12.5×12.5 cm2) are fabricated at Trina Solar on n-type Cz substrates with a resistivity of 2.5 ω·cm. A champion cell with an in-house measured efficiency of 20.5% is obtained, demonstrating a high potential in commercializing the advanced cells developed in this work. Finally, simulations reveal that further improvements in cell efficiency are to be mainly achieved through further optimisations of the rear side contact geometry and rear surface passivation.