Surface plays a crucial role in the performance of crystalline silicon (cSi) based solar cells as it affects both electrical and optical properties. To minimize reflection from the flat surface and thus improve light trapping, the cSi wafers must be textured. For mono-cSi cells, anisotropic alkaline etchants are commonly utilized to create pyramids on the surface. However, this method is not viable for multi-crystalline silicon (mc-Si) wafers due to the presence of different and random crystallographic orientations. In this work, we employed laser texturing, which is an isotropic texturing process, as an alternative texturing method for mc-Si wafers. This approach utilizes a laser process to create pits on the cSi surface. The laser’s processing parameters were justified by performing a series of experiments. After texturing, physical (ultrasonic bath with deionized water) and chemical (in KOH with two different concentrations of 1 and 20%) cleanings with different durations were performed which were essential to remove laser-induced damages and other residues from the surface. In order to evaluate the optical response of the textured surfaces, weighted reflection values were measured and correlated with scanning electron microscopy (SEM) images of the textured features before and after post-texturing cleaning step. An impressive low weighted reflection of only 4.2% was measured from laser textured mc-Si with anti-reflection coating after optimizing the laser and post-texturing processes. Moreover, an implied open-circuit voltage (iVoc) of up to 692 mV was achieved by passivating the laser-textured surfaces by Al₂O₃.

The texturing of silicon surfaces is a well-known method of reducing the reflection from the surface of crystalline Si solar cell devices. With the utilization of diamond wires in recent advances in wafer slicing technology, surface texturing for the multi-crystalline Si wafers by the traditional acid-based texturing technique has become difficult. Metal-Assisted Etching (MAE) has been shown to be a promising and low-cost alternative to the traditional acid-based isotropic texturing. This paper reports, for the first time, a new single-step Ni-assisted etching technique to obtain nano-scale porous structures, that is, black silicon on multi-crystalline wafers. We observed lower reflection results in comparison with standard isotropic texturing using a standard acid solution. The structural and optical properties of the surface were identified through reflection measurements and scanning electron microscopy imaging. As a final step, the optimized texturing process was applied to multi-crystalline solar cell devices and showed promising results regarding cell performance parameters.