Solution-Crystalized AgBiS₂ Films for Solar Cells Generating a Photo-Current Density Over 31 mA cm^-2

In response to the toxic heavy metal absorbers in perovskite solar cells (PSCs), this work focuses on the development of an environmentally friendly simple solution-processed infrared (IR) absorber. In this work, a simple solution-crystallized IR-absorbing AgBiS₂ film is reported by spin-coating silver, bismuth nitrates, and thiourea dissolved in dimethylformamide (DMF) to produce thick AgBiS₂ film. Extensive optimization of the precursor concentrations thicknesses and conductive substrates used allow for obtaining 250 nm AgBiS₂ film with different crystal sizes. When applied as an absorber in solar cells, solution-crystalized AgBiS₂ thick film delivers an extraordinarily high current density of over 31 mA cm^-2. The devices show high stability under continuous 100 mW cm^-2 illumination and when stored in the dark for more than six months. When the AgBiS₂ layer is fabricated in a gradient fashion combining one layer of 0.25 m and three layers of 0.5 m precursor concentrations, the efficiency of 5.15% is registered which is the highest reported for the simple solution-crystallized AgBiS₂ films.