Photo-electrochemical characterization of CIGSn lamellar compounds: potential candidates for photoinduced applications

• Published in: Electrochimica acta 2025-01, Vol.511, p.145391, Article 145391
• Main Authors: Belhcen, Amal, Renaud, Adèle, Guillot-Deudon, Catherine, Arzel, Ludovic, Corraze, Benoit, Barreau, Nicolas, Jobic, Stéphane, Caldes, Maria Teresa
• Format: Article
• Language: English
• Subjects: Ambipolarity; Chemical Sciences; CIGSn; Electronic structure; Flat band potential
• ISSN: 0013-4686
• DOI: 10.1016/j.electacta.2024.145391

•CIGSn chalcogenides appear as promising candidates for visible light photocatalysis.•These lamellar semiconductors reveal n-type or ambipolar behavior.•CIGSn compounds exhibit a low charge carrier density and high resistivity.•Ambipolar CIGSn photocatalysts could enhance the efficiency of catalytic reactions. Metal chalcogenide semiconductors are being widely investigated for applications in solar energy conversion, such as photovoltaics and visible light photocatalysis. Herein, an initial assessment of potentialities of new lamellar chalcogenides named CIGSn is provided, while comparing them with that of the well-known CIGS chalcopyrite. The main difference between CIGS and CIGSn compounds concerns their electronic properties and more precisely the nature of charge carriers. Cu0.32In1.74Ga0.84S4 (CIGS4) is an n-type semiconductor, unlike the chalcopyrite CuIn0.7Ga0.3S2 (CIGS) that is a p-type semiconductor. More noticeable, Cu1.44In2.77Ga0.76S6 (CIGS6) and in a lesser extent Cu0.65In1.75Ga1.4S5 (CIGS5), exhibit an ambipolar character with a slight predominance of electron transport. The Fermi levels of all lamellar CIGSn compounds are similar (-4.5 eV) and higher that of the chalcopyrite CIGS (-5.1 eV). In addition, the charge carrier densities of CIGSn compounds (1014–1017 cm−3) are significantly lower than that of CIGS (1020 cm−3), which is consistent with their higher resistivity. Photoluminescence measurements and OCP decays suggest much more in-gap defect states in the lamellar compounds. These results suggest that CIGSn compounds would not be suitable for photovoltaic applications. Nevertheless, their energy bands show an interesting positioning, with respect to redox potentials involved in water splitting and CO2 reduction. In addition, ambipolarity could enhance the efficiency of catalytic reactions, because a type of minority charge carriers does not limit the charge transport. [Display omitted]