Highly Efficient Copper-Zinc-Tin-Selenide ( CZTSe) Solar Cells by Electrodeposition

Abstract

Highly efficient copper-zinc-tin-selenide (Cu2ZnSnSe4; CZTSe) thin-film solar cells are prepared via the electrodepostion technique. A metallic alloy precursor (CZT) film with a Cu-poor, Zn-rich composition is directly deposited from a single aqueous bath under a constant current, and the precursor film is converted to CZTSe by annealing under a Se atmosphere at temperatures ranging from 400 degrees C to 600 degrees C. The crystallization of CZTSe starts at 400 degrees C and is completed at 500 degrees C, while crystal growth continues at higher temperatures. Owing to compromises between enhanced crystallinity and poor physical properties, CZTSe thin films annealed at 550 degrees C exhibit the best and most-stable device performances, reaching up to 8.0% active efficiency; among the highest efficiencies for CZTSe thin-film solar cells prepared by electrodeposition. Further analysis of the electronic properties and a comparison with another state-of-the-art device prepared from a hydrazine-based solution, suggests that the conversion efficiency can be further improved by optimizing parameters such as film thickness, antireflection coating, MoSe2 formation, and p-n junction properties.