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 °C to 600 °C. The crystallization of CZTSe starts at 400 °C and is completed at 500 °C, while crystal growth continues at higher temperatures. Owing to compromises between enhanced crystallinity and poor physical properties, CZTSe thin films annealed at 550 °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.

Compositional and Interfacial Modification of Cu2ZnSn(S,Se)4 Thin‐Film Solar Cells Prepared by Electrochemical Deposition

“…The EQE curves clearly show that the absorption edge moves towards shorter wavelengths (i.e.,l arger bandgap) with increasing Sc ontents. The bandgap energies calculated from the EQE curves (inset of Figure 2a)a re 1.03, 1.07, 1.14, and 1.18 eV for the CZTSSe thin films with Sc ontentso f0 ,1 5, 25, and 31, respectively.T he bandgap energy of the pure CZTSe is consistent with previous www.chemsuschem.org results, [1,7] and the bandgape nergies of CZTSSe thin films are consistentw ith those estimated from the EDS and XRD analyses. This result, again, shows that the bandgape nergy of the CZTSSet hin films can be controlled very precisely through the Scontent in the CZTSSesolid solution.…”

“…[7] The electrochemical deposition was performed using at wo-electrode system with aM o-coated soda-lime glass substrate (3 4 cm 2 ,w orking electrode) and aP tp late (counter electrode). The films were deposited at ac onstant current density of À1.18 mA cm À2 for 1200 s. Before the deposition, the substrates were cleaned with acetone, ethanol, and deionized water followed by drying in an itrogen stream.…”

Effect of sulfurization time on the properties of copper zinc tin sulfide thin films grown by electrochemical deposition

“…Two of the most important parameters to prepare CZTS are sulfurization time and annealing temperature. Before annealing, a drying step is carried out at 200–300 °C to maximize solvent evaporation8. However, some reports indicate that intermediates like binary sulfide of the constituent elements, bimetallic alloys or ternary Cu x SnS y can form at these temperatures9.…”

Optical and surface probe investigation of secondary phases in Cu 2 ZnSnS 4 films grown by electrochemical deposition

“…Lee et al reported that CZTS thin-film solar cells could achieve a 2% conversion efficiency [19] when soaked in an aqueous KCN solution, and we had improved the efficiency to higher than 5%. We use the same process with the CZTS samples, and very recently, we had achieved a conversion efficiency of 8% for CZTSe solar cells by applying selenization via KCN etching [20].…”