Solution processed CuAgS absorber layers from a thiol-amine-based ink

Robust and environmentally stable absorber layers are essential for the development of durable and cost-effective solar energy conversion, especially as demand for renewable energy continues to grow. Stromeyerite (CuAgS), a naturally occurring steely grey mineral, is an intermediate compound in the pseudo-binary Cu₂S–Ag₂S phase diagram and crystallizes in the orthorhombic Cmc2₁ space group. To date, there have been no reports investigating the photoactivity of CuAgS and solution processed thin films have been under-characterized or contain Cu_2–xS impurities. Here, we report the use of a thiol-amine solvent mixture to dissolve bulk Cu₂O, Ag₂O, and elemental sulfur, forming a precursor ink that can be solution-processed into phase-pure CuAgS thin films via a simple dissolve-and-recover method. The resulting films exhibit a direct optical band gap of E_g = 1.16 eV and an absorption coefficient exceeding 10⁴ cm⁻¹ across the visible spectrum. The material also demonstrates a strong photoelectrochemical current response, indicating its potential for solar energy conversion applications.