Over 21% Efficiency of n-Type Monocrystalline Silicon PERT Photovoltaic Cell With Boron Emitter

Abstract

We have developed an n-type monocrystalline silicon photovoltaic cell achieving the conversion efficiency of 21.3% by passivated emitter and rear totally diffused structure with a total area of 239 cm2. The center area of the cell showed 21.7% (226.3 cm2). The main developments for the cell related to an emitter are a boron diffusion process and a passivation process of the boron layer. The developed cells contain a deeply diffused and lightly doped boron emitter with a high-quality surface passivation layer to obtain high efficiency. An atmospheric pressure chemical vapor deposition (APCVD) process is used for the fabrication of a boron emitter. This process is suitable for mass production lines. An atomic layer deposition Al2O3 layer is applied for a passivation of the boron layer. In addition, the ohmic contacts between the cell and electrodes are improved by changing a temperature profile for an electrode firing process.