Dimethyl Sulfoxide Vapor-Assisted Cs₂AgBiBr₆ Homogenous Film Deposition for Solar Cell Application

Despite persistent stability and toxicity challenges, hybrid lead halide perovskites are promising semiconductors for optoelectronic applications such as photovoltaics. Double perovskites have recently been proposed as alternatives to hybrid lead halide perovskites. Cs2AgBiBr6 has been especially promising thanks to its high stability and nontoxicity. For achieving high performance, it is necessary to prepare well-crystallized perovskite absorbers. This study utilizes a postannealing process to treat perovskite films under three different annealing conditions; annealing the Cs2AgBiBr6 films 1—under ambient conditions (thermal annealing), 2—in dimethyl sulfoxide (DMSO) vapor (solvent annealing), and 3—inside a N2-filled glovebox (glovebox annealing). The observations indicate that the DMSO vapor significantly affects the growth of the film. Therefore, solvent annealing of the Cs2AgBiBr6 films at 250 °C demonstrates a uniform and pinhole-free film with a large grain size. Besides, the crystallinity of the Cs2AgBiBr6 film is improved, based on the increased intensity of XRD diffraction peaks of the Cs2AgBiBr6 film synthesized by solvent-annealing. Solar cells based on the DMSO-treated films provide a power conversion efficiency (PCE) of more than 2.4%. The solvent-annealing procedure leads to a comparable efficiency and high-quality film, which is promising for application in Pb-free perovskite solar cells.