Green scalable vapor texture etching for multicrystalline silicon wafers

• Published in: Progress in photovoltaics 2020-10, Vol.28 (10), p.993-1000
• Main Authors: Sun, Pei‐Yu, Tsai, Pi‐Chen, Liang, Po‐Yu, Hsu, Hsiao‐Ping, Sutejo, Agustina, Yang, Allen, Lan, Chung‐Wen
• Format: Article
• Language: English
• Subjects: Acids; Diamonds; Emitters; Etching; multicrystalline; Photovoltaic cells; Production lines; reflectivity; Silicon; Silicon wafers; Slicing; Solar cells; Texture; Texturing; vapor; Wafers
• ISSN: 1062-7995; 1099-159X
• DOI: 10.1002/pip.3302

In recent years, the low‐cost diamond‐wire (DW) slicing has been widely used for single‐crystalline silicon (sc‐Si) wafers, and this makes sc‐Si solar cells very attractive to the market. On the contrary, the adoption of DW slicing for multicrystalline (mc‐Si) wafers is troublesome because of poor texturing quality in the existing production lines using acid solutions. We have developed a vapor texture etching (VTE) process with the combination of both acid and reacted vapors for DW sliced mc‐Si wafers. The etching process was rather simple and low cost. More importantly, the acid usage was low and recyclable, so that the acid emission was low as well. Its scale‐up was easy and straightforward. In this lab‐scale reactor, more than 50 full‐size wafers could be processed each time. The etched wafers had uniform appearance and low reflectivity, around 10%. After the nanostructure pores were enlarged by post treatments to minimize surface recombination, the full‐size mc‐Si solar cell fabricated by Solartech could achieve an efficiency of 19.7% using the Passivated Emitter and Rear Contact (PERC) structure, which was comparable with the average production efficiency. We developed a vapor texture etching (VTE) process that was rather simple and low cost. Its scale‐up was easy and straightforward. In this lab‐scale reactor, more than 50 full‐size wafers could be processed each time. The etched wafers had uniform appearance and low reflectivity, around 10%. After the nanostructure pores were enlarged by post treatments to minimize surface recombination, the mc‐Si solar cell could achieve an efficiency of 19.5% using the Passivated Emitter and Rear Contact (PERC) structure.