High Recovery of Selenium from Kesterite‐Based Photovoltaic Cells

• Published in: European journal of inorganic chemistry 2020-06, Vol.2020 (22), p.2203-2209
• Main Authors: Asensio, Maria Pilar, Abás, Elisa, Pinilla, Jose Luis, Laguna, Mariano
• Format: Article
• Language: English
• Subjects: Absorbers; Ascorbic acid; Chemical elements; Circular economy; Economic conditions; Heat treatment; Inorganic chemistry; Kesterite; Oxidation; Photovoltaic cells; Reagents; Redox chemistry; Reduction; Selenium; Selenium oxides; Waste recovery
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.202000261

The use of photovoltaic cells is constantly increasing and, in particular, a new generation of thin‐film photovoltaic (PV) cells is under development. The absorber of these new cells, kesterite (CZT(S)Se), is composed of abundant chemical elements. Nonetheless, the development of the recycling process for these elements is indispensable for circular economy. This research is focused on the recovery of selenium by thermal oxidation and subsequent reduction. Thus, recycling of selenium has been firstly studied on synthetic kesterite and then validated in a real sample of kesterite extracted from glass‐based PV cells. The best results were obtained in a vertical tubular furnace at 750 °C with an input of 20 mL/min of air. The posterior reduction process of selenium oxide was achieved by ascorbic acid, a common and economic reagent. Real kesterite was extracted from PV cells by thermal treatment at 90 °C for 1 hour to remove the encapsulant and ulterior treatment with HCl for the release of kesterite absorber. Optimal conditions from synthetic kesterite were applied to a real sample, recovering more than 90 % of selenium with a purity of 99.4 %. Recovery of selenium from kesterite (Cu2ZnSn(S,Se)4) thin film photovoltaic cells by oxidation in a vertical tubular furnace at 750 °C with an input of 20 mL/min of air is described. The only volatile oxide, SeO2, condenses in the cold part of the oven. The posterior reduction process was achieved by ascorbic acid, in a Circular Economy process.