Effects of different laser modified surface morphologies and post-texturing cleanings on c-Si solar cell performance

Performance of crystalline Silicon solar cells depends on numerous factors. One key factor is a surface structure which can restrict electrical and optical properties due to recombination of generated carriers and reflection of incident light. Surface texturing reduces reflection from a flat surface which increases absorption of light. Anisotropic alkaline etchants are commonly used for texturing mono-crystalline Silicon wafers which produce pyramid structures on the surface. Because of randomly oriented crystallographic grains, this method is not feasible for multi-crystalline Silicon wafers. Here, an alternative texturing process using a laser system is proposed. Laser beam creates vertical and horizontal grooves on the surface in which the intersections are for a light trapping purpose. Laser parameters are determined experimentally to have the lowest reflection. Next, chemical post-texture cleaning is performed to remove laser-induced damages and other residues. Finally, samples went through general solar cell fabrication steps. For characterizations, weighted reflection is measured and correlated with Scanning Electron Microscopy images of a textured surface to evaluate the performance of texturing and post-texture cleaning. To examine fabricated solar cells' performance, I-V curve and External Quantum Efficiency are measured. Results indicate that proposed processes lead to an improved efficiency compared to reference samples. (c) 2019 Elsevier Ltd. All rights reserved.