ECN n-type silicon solar cell technology: An industrial process that yields 18.5%

There is currently much interest in n-type solar cells because of the advantages of this material. N-type material is expected to be more favourable for obtaining high efficiencies than p-type doped substrates. We have developed a process for n-type solar cells for large area multicrystalline and monocrystalline silicon wafers. The production process is based on industrial processing steps such as screen-printed metallization and firing through. The surfaces of these cells are passivated with a layer stack consisting of SiO₂ and SiN_x where the former is created by a wet chemical process and the latter by inline PECVD. We demonstrate that the surface passivation can be improved with an alternative wet chemical process for creating the SiO₂ layer. This new process results in an enhancement of the implied V_oc of unmetallized cells as measured by quasi-steady-state photoconductance (QSSPC) and the V_oc of completed cells. The process Improvements have yielded a new record efficiency of 18.5 % (for a particular rear reflection surface) that was independently confirmed by Fraunhofer ISE CalLab.