Atmospheric pressure chemical vapor deposited aluminium oxide / silicon nitride stacks for PERC and PERT solar cell concepts with high passivation quality

Abstract

PERC (Passivated Emitter and Rear Cell) cells based on p-type crystalline Si and PERT (Passivated Emitter, Rear Totally diffused) cells based on n-type crystalline Si are getting more and more attractive in the commercial solar cell market. As a result of the highly competitive market, a low-cost production reached by high through-put and low upkeep is necessary. Atmospheric chemical vapor deposition (APCVD) tools fulfill these requirements and provide necessary high layer quality for high-efficiency solar cell production. Aluminum oxide (AlOx) layers may in certain situations reach a surface passivation quality higher than atomic layer deposition (ALD) based AlOx layers. In this contribution we demonstrate excess minority charge carrier lifetime values eff up to 15 ms (surface recombination velocity S <0.3 cms-1) on n-type Czochralski-Si for undiffused samples as well as emitter saturation current density values j0e down to 21 fA/cm2 on a 65 Ω/sq p+ emitter for fired AlOx/SiNy:H stacks, common to PERC and PERT solar cell designs, respectively. We also determined the influence of reaction energy depending on heat delivery during APCV-deposition on the layer growth leading to a high temperature stable, low-pinhole density and blistering free layer (stack).