Surface texturization of multicrystalline silicon with electrochemical etching in NaOh/H2O solution for solar cell application

Abstract

Preparation of the anti-reflective (AR) texture on crystalline silicon (c-Si) surface is an effective way to improve the c-Si solar cell performance. The surface texturization of multicrystalline silicon (mc-Si) is usually performed by chemical etching (CE) in HNO3/HF/H2O solution and the obtained surface reflectance (R) is normally higher than 20%. Here, a novel method based on electrochemical etching (ECE) in NaOH/H2O solution was proposed for the surface texturization of mc-Si. Via the proposed alkaline ECE process, a macroporous texture with the pore feature size of about 100-200 nm could be prepared on the mc-Si wafer surface, reducing the weighted average surface reflectance (Ra) in a wide wavelength range of 400-1100 nm to be about 18.5%. To ensure the complete removal of the damaged layer on the mc-Si surface, the ECE process could be performed on mc-Si pretreated by the traditional CE process in HNO3/HF/H2O solution. Such two-step way resulted in a hierarchical texture with the macroporous structure superimposed onto micrometer-sized CE pits, which lowered the above Ra to be about 17.5% further. As a comparison, Ra was high up to 24.8% if only the traditional acidic CE process was carried out individually. The results indicated that such a novel ECE process in NaOH/H2O solution had a great application potential to make the AR texture for the mc-Si solar cells.