Exploring the potential of powder-to-film processing for proof-of-concept BaZrS3 perovskite solar cells

Lead-free chalcogenide perovskites, such as BaZrS3, manifest as strong candidates to replace toxic metals-containing halide perovskites in optoelectronic applications, but the formation of high-quality films for photovoltaic applications remains a major challenge for now, since very high temperatures are needed to fully crystalize the compound. To circumvent this issue, liquid-phase synthesis, through direct fabrication of perovskite nanocrystals dispersed in an organic solvent or a conversion of a pre-crystalline powder to an ink, has been suggested as a viable strategy for low-temperature processing. However, both cases result in films which cannot be used in the fabrication of solar cells. Herein, in this work, we adopt the latter approach, and convert BaZrS3 particles, from solid-state synthesis to a stable colloidal dispersion in a 1-Methyl-2-pyrrolidone (NMP)-oleylamine (OA) mixture. We report a detailed identification of the structural changes of this transformation with a large range of crystallographic, spectroscopic and microscopic techniques. Then, we evaluate the feasibility of the process for the fabrication of films. BaZrS3 infiltrated in mesoporous TiO2/FTO transparent glass substrates were used as photolectrodes in solar cells and proof-of concept devices were constructed in conjunction with I3-/I- redox electrolyte for the first time in literature, reaching a mean PCE of 0.11% and a FF of 61%. We believe that this work will pave the way towards the systematic use of BaZrS3 (or other similar chalcogenide perovskites) in solar cells and other relevant optoelectronic devices.