Rear passivated mc-Si solar cells textured by atmospheric pressure dry etching

In this contribution, atmospheric pressure dry etching (ADE) texture is integrated into a passivated emitter and rear cell (PERC) process. In order to make the texture suitable for the solar cell processing, two post-etching processes (inverted pyramid, spherical cap) are implemented and compared. The passivation of the front surface could be improved substantially by the introduction of an Al2O3 layer deposited via atomic layer deposition under the classical antireflection coating SiNX. The impact of the addition of the Al2O3 layer on the contact resistance cannot be neglected and becomes significant for thicknesses higher than 4 nm. Multicrystalline silicon (mc-Si) PERC solar cells are fabricated and measured, leading to a maximum efficiency of about 18.6% for the acidic texture, and for both posts-processed dry chemical etching (ADE) textures. No current gain for the ADE textured wafer compared to the acidic texture could be observed on cell level due to an inhomogeneous etching. However, a gain of 0.4 mA/cm2 for the ADE texture was calculated from local EQE measurements. ADE texture presents therefore 2 advantages: compatibility to diamond wire sawing and a potential current gain for PERC solar cell structure.